1049 Hydrogen Peroxide Crops

The National Organic Program (NOP) final rule currently allows the use of hydrogen peroxide in organic crop 15 production under 7 CFR §205.601(a)(4) as an algicide, disinfectant, and sanitizer, as well as 7 CFR §205.601(i)(5) 16 for plant disease control as a fungicide. This report provides targeted technical information and augments the 17 1995 Technical Advisory Panel Report on hydrogen peroxide for the National Organic Standards Board’s sunset 18 review of the substance.

Composition of the Substance:

Hydrogen peroxide is a small inorganic molecule comprised of two hydrogen atoms and two oxygen 24 atoms with a molecular formula of H2O2. As a peroxy compound, hydrogen peroxide contains a highly 25 reactive oxygen-oxygen single bond (Figure 1). Although modern manufacturing practices allow the 26 production of pure hydrogen peroxide, the substance is sold for most agricultural, industrial and 27 residential uses as a solution in water. Hydrogen peroxide fungicides are typically formulated as 28 concentrates (approximately 30% H2O2) and diluted with water to generate working solutions of 0.01–0.3% 29 H2O2 (US EPA, 2014).

Source or Origin of the Substance:

Commercially available hydrogen peroxide is industrially produced using the anthraquinone autoxidation 34 (AO) process. The AO method involves initial catalytic reduction of an alkyl anthraquinone with hydrogen 35 to form the corresponding hydroquinone. Subsequent autoxidation of the hydroquinone intermediate in 36 air regenerates the anthraquinone with concomitant liberation of hydrogen peroxide (Goor, 2007). As 37 shown in equation 1, the simplified overall reaction involves direct combination of gaseous hydrogen (H2) 38 and oxygen (O2). See Evaluation Question #2 for details regarding the anthraquinone AO process, older 39 production methods, and developing technologies for hydrogen peroxide synthesis.

Properties of the Substance:

Hydrogen peroxide is a weakly acidic, nearly colorless and clear liquid with solubility in water at all 43 proportions. The hydrogen and oxygen atoms within the hydrogen peroxide molecule are covalently bound in a nonpolar H–O–O–H structure having association (hydrogen bonding) somewhat less than that 45 found in water. Table 1 below summarizes the chemical and physical properties for hydrogen peroxide.

Specific Uses of the Substance:

Hydrogen peroxide and other biopesticidal peroxy compounds are used as algicides and fungicides in 52 greenhouses and horticultural settings, applied to greenhouse structures and surfaces as well as 53 greenhouse seeds, soils and plants (US EPA, 2009b). The substance is also used in some turf and orchard 54 settings. As a broad-spectrum fungicide, hydrogen peroxide pesticide products are applied for the 55 prevention and control of plant pathogenic diseases. Hydrogen peroxide products may be used as a pre-56 plant dip treatment for root disease and stem rot disease caused by Pythium, Phytophthora, Rhizoctonia, 57 Fusarium or Thielaviopsis on seeds, seedlings, bulbs or cuttings; soil drench for the control of soil-borne 58 plant at the time of seeding or transplanting, as well as a preventative treatment throughout the plant’s life; 59 and a foliar treatment for field grown crops, crops grown in commercial greenhouses or crops grown in 60 other similar sites (BioSafe, 2010).

The OxiDate® product label and agricultural extension resources indicate that hydrogen peroxide 62 treatments may be effective in preventing or controlling late-season outbreaks of grape diseases, such as 63 powdery mildew, downy mildew and bunch rot (BioSafe, 2010; Schilder, 2011). Indeed, hydrogen peroxide 64 is particularly effective against fungal diseases on plant surfaces, including powdery mildew, because the 65 substance only contacts the surface of infected plants and not deeper into infected plant tissues. Hydrogen 66 peroxide has also been employed in organic apple production to combat the fungus Venturia inaequalis, the 67 pathogen responsible for apple scab disease (Phillips, 2005). Likewise, hydrogen peroxide has been 68 included in lists of alternative substances for downy mildew control in cucurbits (Kuepper, 2003). In addition to field and greenhouse applications, hydrogen peroxide provides control of postharvest diseases 70 of strawberries and oranges, such as Botrytis cinerea, Rhizopus stolonifer, Penicillium digitatum, and 71 Penicillium italicum (El-Mougy, 2008), as well as pink rot of potato fungus, Phytophthora erythroseptica (Al-72 Mughrabi, 2006). Some greenhouse managers also use hydrogen peroxide in irrigation water recirculation 73 systems to prevent the spread of soil borne disease organisms (Newman, 2004).

Hydrogen peroxide is also found in numerous health care and consumer products. According to the 75 Centers for Disease Control and Prevention, “commercially available 3% hydrogen peroxide is a stable and 76 effective disinfectant when used on inanimate surfaces,” and is used at concentrations of 3–6% for spot-77 disinfecting ventilators, endoscopes and fabrics in patients’ rooms (CDC, 2008). The substance is also used 78 as a topical disinfectant and antimycotic to sterilize contact lenses. Small amounts of hydrogen peroxide 79 are used in cosmetic preparations such as hair colorations and bleaching formulations. Indeed, hydrogen 80 peroxide is the active ingredient in color-safe household bleaches and carpet and hard-surface cleaners. 81 Hydrogen peroxide and other inorganic peroxo compounds are commonly employed as peroxide sources 82 in oral hygiene and teeth whitening products. Topical solutions containing 3% hydrogen peroxide are sold 83 as over-the-counter drugs for antisepsis and disinfection in the United States (Eul, 2001).

Beyond agriculture, disinfection and residential use, hydrogen peroxide is also used in a variety of 85 industrial processes. Hydrogen peroxide is used in the textile industry for bleaching cotton, linen, bast fiber 86 (soft, woody fiber obtained from plant stems), wool, silk, polyester fiber and polyurethane fiber. Likewise, 87 the substance is used to bleach sulfate and sulfite cellulose, wood pulp, and wastepaper, and to brighten 88 wood veneers and wooden structures in the pulp and paper industry. The chemical industry employs 89 hydrogen peroxide for the production of peroxy compounds, such as sodium perborate, sodium 90 percarbonate, metallic peroxides, or percarboxylic acids. In organic chemistry, hydrogen peroxide is used 91 for epoxidation and hydroxylation (manufacture of plasticizers and stablizers for the plastics industry), 92 oxidation (manufacture of amine oxides as surfactants for detergents), oxohalogenation, and initiation of 93 polymerization. BASF and Dow Chemical Company recently developed a process for the production of 94 propylene oxide (C3H6O) using hydrogen peroxide. Lastly, hydrogen peroxide is used to polish copper, 95 brass and other copper alloys; for etching and cleaning printed circuit boards; to clean silicon wafers used 96 in the manufacture of silicon semiconductors; for in situ leaching in underground uranium mining; and for 97 environmental protection applications (i.e., to detoxify mining wastewater effluents and deodorize sulfur-98 containing effluents) (Eul, 2001; Goor, 2007).

Approved Legal Uses of the Substance:

The US Environmental Protection Agency (US EPA) first registered pesticidal hydrogen peroxide products 101 for use in the United States in 1977 (US EPA, 2009b). Based on a recent search of the Pesticide Product 102 Information System (PPIS), there are currently 164 registered formulations containing hydrogen peroxide 103 as an active ingredient (US EPA, 2014). In agriculture, hydrogen peroxide pesticides are used primarily as 104 microbiocides on a variety of agricultural use sites, such as greenhouses, horticultural establishments and 105 some orchards. Currently registered hydrogen peroxide products are labeled as algicides, antifoulants, 106 bacteriocides/bacteriostats, disinfectants, fungicides/fungistats, nematicides, microbiocides/microbiostats, 107 molluscicides, sporicides, sanitizers, sterilizers, tuberculocides and virucides. Most if not all of the 108 fungicides containing hydrogen peroxides are also registered for antimicrobial use patterns (US EPA, 109 2009b). According to 40 CFR 180.1197, an exemption from the requirement of a tolerance has been 110 established for residues of hydrogen peroxide in or on all food commodities at the rate of less than or equal 111 to one percent (≤ 1%) hydrogen peroxide per application on growing and postharvest crops.

In the United States, the Food and Drug Administration (FDA) has established legal uses of hydrogen 113 peroxide in food, cosmetic and drug products. According to a recent Agency response, FDA believes that 114 most peroxide-containing tooth whiteners would meet the definition of a cosmetic under the Food, Drug 115 and Cosmetic (FD&C) Act, but acknowledged that some of these products may be regarded as drugs (FDA, 116 2014). FDA postponed a final decision on the status of peroxide-based tooth whitening products since “a 117 better understanding of the mechanisms of action, conditions of use, safety, and formulation of specific 118 peroxide-containing tooth whitener products is necessary to determine whether such products also meet 119 the definition of drug under the FD&C Act” (FDA, 2014). For the time being, FDA will continue using a 120 case-by-case regulatory approach based on the claims associated with individual whitening products (Gaffney, 2014). Hydrogen peroxide is an FDA-approved indirect food additive allowed for use only as a 122 component of adhesives (21 CFR 175.105). The substance is also Generally Recognized as Safe (GRAS) 123 when used as a bleaching agent in animal drugs, feeds and related products in accordance with good 124 manufacturing or feeding practice (21 CFR 582.1366). According to 21 CFR 184.1366, hydrogen peroxide is 125 a direct food additive affirmed as GRAS when the ingredient is used to treat food only within the following 126 limitations:

• Milk – For use during the cheesemaking process as permitted in the appropriate standards of 128 identify for cheese and related cheese products at a maximum treatment level of 0.05%,
• Whey – For use during the preparation of modified whey by electrodialysis methods at a 130 maximum treatment level of 0.04%,
• Dried eggs, dried egg whites, and dried egg yolks – Oxidizing and reducing agent in an amount 132 sufficient for the purpose,
• Tripe – Bleaching agent,
• Beef feet – Bleaching agent,
• Herring – Bleaching agent,
• Wine – Oxidizing and reducing agent in an amount sufficient for the purpose,
• Starch – Antimicrobial agent at a maximum treatment level of 0.15%,
• Instant tea – Bleaching agent in an amount sufficient for the purpose,
• Corn syrup – Used to reduce sulfur dioxide levels in the finished corn syrup at a maximum 140 treatment level of 0.15%,
• Colored (annatto) cheese whey – Bleaching agent at a maximum treatment level of 0.05%,
• Wine vinegar – Used to remove sulfur dioxide from wine prior to fermentation to produce vinegar 143 at an amount sufficient for the purpose,
• Emulsifiers containing fatty acid esters – Bleaching agent at a maximum treatment level of 1.25%.

Action of the Substance:

As a pesticide class, fungicides kill by damaging cell membranes, inactivating critical enzymes or proteins, 147 and/or interfering with key metabolic processes such as respiration. Specialized plant enzymes known as 148 peroxidases produce hydrogen peroxide for disease control, and are associated with fungal cell wall 149 degradation and plant defense signaling as part of the Salicylic Acid pathway (Matheron, 2001). In general, 150 hydrogen peroxide works by producing destructive hydroxyl free radicals that can attack membrane 151 lipids, DNA and other essential cell components (CDC, 2008). Catalase enzymes produced by aerobic 152 organisms and facultative anaerobes that possess cytochrome systems can protect cells from metabolically 153 produced hydrogen peroxide by degrading the substance to water and oxygen. This defense mechanism is 154 overwhelmed by the concentration used for disinfection or, in the case of agriculture, fungicidal 155 applications to crops and soils (CDC, 2008).

Combinations of the Substance:

Various active and inert ingredients may be added to commercially available fungicides and disinfectants 158 containing hydrogen peroxide. Sixty-eight out of the 164 currently registered pesticide products containing 159 hydrogen peroxide also contain peroxyacetic acid as an active ingredient at concentrations ranging from 160 0.08 to 15.2 percent (US EPA, 2014). According to USDA organic regulations, peroxyacetic acid is permitted 161 in hydrogen peroxide formulations at a concentration of no more than 6% as indicated on the pesticide 162 product label (7 CFR 205.601(a)(6) and (i)(8)). The active ingredients hydrogen peroxide, peroxyacetic acid 163 and caprylic acid are co-formulated in a small number of commercial disinfectant products. Mono- and di-164 potassium salts of phosphorous acid are co-formulated with hydrogen peroxide as the active ingredients in 165 one broad-spectrum fungicide product. Other active substances that are combined with hydrogen peroxide 166 in registered disinfectants include quaternary ammonium compounds (e.g., alkyl dimethyl ethylbenzyl 167 ammonium chloride), sodium nonanoyloxybenzene sulfonate, and metallic silver (US EPA, 2014).

The labels of most registered fungicides and disinfectants containing hydrogen peroxide list “other 169 ingredients” for the inert portion of the formulation. Water is the primary inert ingredient in hydrogen 170 peroxide pesticide products. In addition, a small number of product labels list salicylic acid and phosphoric 171 acid (two products), benzyl alcohol (two products), acetic acid (one product), and citric acid and 1-(1-butoxypropan-2-yloxy)propan-2-ol (one product) as formulated inert ingredients (US EPA, 2014). Product 173 formulations are considered confidential business information, and companies may reformulate products 174 following the registration process. As a result, it is not always possible to know the identity of adjuvants 175 and other inert ingredients used in formulated products.

Historic Use:

The US Environmental Protection Agency (US EPA) first registered pesticidal hydrogen peroxide products 180 for use in the United States in 1977 (US EPA, 2009b). Since its registration, hydrogen peroxide has been 181 formulated in an increasing number of pesticide products, with 164 hydrogen peroxide disinfectants and 182 fungicides currently registered for use (US EPA, 2014). Historically, agricultural disinfectants containing 183 hydrogen peroxide have been used for the disinfection of livestock housing surfaces and production 184 equipment, production surfaces in greenhouses, crop production equipment, water storage tanks, 185 irrigation lines and food contact surfaces in processing facilities. Hydrogen peroxide fungicide solutions 186 have been used as foliar sprays, soil drenches and seed treatments for annual (e.g., cucurbits) and perennial 187 (e.g., grapes, apples) crops in field and greenhouse settings (US EPA, 2014).

Organic Foods Production Act, USDA Final Rule:

USDA organic regulations currently allow the use of hydrogen peroxide in organic crop production under 190 7 CFR §205.601(a)(4) as an algicide, disinfectant and sanitizer, and under 7 CFR §205.601(i)(5) for plant 191 disease control as a fungicide. Likewise, hydrogen peroxide is also permitted for use in organic livestock 192 production as a disinfectant, sanitizer and medical treatment (7 CFR 205.603(a)(13)). Lastly, synthetic 193 hydrogen peroxide may be used as an ingredient in or on processed products labeled as “organic” or 194 “made with organic (specified ingredients or food group(s)).” (7 CFR 205.605(b)).

International

A subset of the international organizations surveyed have provided guidance on the application of 197 hydrogen peroxide for disinfection and plant disease control in organic crop production. Among these are 198 regulatory agencies (EU and Canada) and independent organic standards organizations (IFOAM and The 199 Soil Association). International organic regulations and standards concerning hydrogen peroxide are 200 described in the following sub-sections.

Canadian General Standards Board

The Canadian General Standards Board allows numerous uses of hydrogen peroxide in organic 203 production. Under Section 4.3: “Crop production aids and materials,” hydrogen peroxide is not allowed in 204 maple syrup production, but is allowed for use as a fungicide. Section 5.3: “Health care and production 205 aids for livestock production” lists pharmaceutical grade hydrogen peroxide for external use as a 206 disinfectant, and food-grade hydrogen peroxide for internal use (e.g., livestock drinking water). Hydrogen 207 peroxide is also listed in Section 7.3: “Food-grade cleaners, disinfectants and sanitizers” that are allowed 208 without mandatory removal of residues, and 7.4: “Cleaners, disinfectants and sanitizers allowed on food 209 contact surfaces including equipment, provided that substances are removed from food contact surfaces 210 prior to organic production” (CAN, 2011).

European Union

According to Annex VII of EU regulation 889/2008, hydrogen peroxide is allowed for cleaning and 213 disinfection of buildings and installations for animal production. Specifically, hydrogen peroxide can be 214 used to satisfy Article 23 (4), which states that “housing, pens, equipment and utensils shall be properly 215 cleaned and disinfected to prevent cross-contamination and the buildup of disease carrying organisms.” 216 Hydrogen peroxide is also permitted for use in the production of gelatin under Section B of Annex VIII: 217 Products and substances for use in production of processed organic food (EC, 2008).

International Federation of Organic Agriculture Movements

Hydrogen peroxide is permitted under Appendix 4 – Table 2 of the IFOAM Norms as an equipment 220 cleanser and disinfectants. In addition, Appendix 5 lists hydrogen peroxide as an approved substance for 221 pest and disease control and disinfection in livestock housing and equipment (IFOAM, 2014). The Norms 222 make not mention of hydrogen peroxide for plant disease control and prevention.

UK Soil Association

The Soil Association standards permit the use of hydrogen peroxide only as a cleaning product for 225 livestock housing areas. No conditions are provided allowing the use of hydrogen peroxide for plant 226 disease control and prevention (Soil Association, 2014).

Evaluation Questions for Substances to be used in Organic Crop or Livestock Production

Evaluation Question #1: Indicate which category in OFPA that the substance falls under: (A) Does the 230 substance contain an active ingredient in any of the following categories: copper and sulfur 231 compounds, toxins derived from bacteria; pheromones, soaps, horticultural oils, fish emulsions, treated 232 seed, vitamins and minerals; livestock parasiticides and medicines and production aids including 233 netting, tree wraps and seals, insect traps, sticky barriers, row covers, and equipment cleansers? (B) Is 234 the substance a synthetic inert ingredient that is not classified by the EPA as inerts of toxicological 235 concern (i.e., EPA List 4 inerts) (7 U.S.C. § 6517(c)(1)(B)(ii))? Is the synthetic substance an inert 236 ingredient which is not on EPA List 4, but is exempt from a requirement of a tolerance, per 40 CFR part 237 180?

(A) The primary use patterns reviewed in this report are the fungicidal applications of hydrogen peroxide. 239 Hydrogen peroxide is also considered an equipment cleanser due to its permitted use as an algicide, 240 disinfectant and sanitizer in organic crop (7 CFR 205.601(a)(4)) and livestock (7 CFR 205.603(a)(13)) 241 production. In fact, OMRI has approved several “cleaning agents” and “equipment cleansers for farms” 242 that contain hydrogen peroxide as the active ingredient.

(B) Hydrogen peroxide is the active substance in several commercial disinfectant and fungicide products, 244 and is therefore not considered an inert ingredient.

Evaluation Question #2: Describe the most prevalent processes used to manufacture or formulate the 246 petitioned substance. Further, describe any chemical change that may occur during manufacture or 247 formulation of the petitioned substance when this substance is extracted from naturally occurring plant, 248 animal, or mineral sources (7 U.S.C. § 6502 (21)).

Virtually all modern production facilities manufacture commercial hydrogen peroxide solutions using 250 large, strategically located anthraquinone autoxidation processes (Eul, 2001). Indeed, improved production 251 methods and facilities based on the anthraquinone (AO) process have recently appeared in the commercial 252 patent literature (Solvay, 2013).

In the AO process, 2-alkyl-9,10-anthraquinones react with hydrogen (H2) in the presence of a transition 254 metal catalyst such as palladium or Raney nickel to form the corresponding hydroquinones (equation 2). 255 Alkyl groups commonly employed in these anthraquinone systems include 2-ethyl, 2-isopropyl, 2-sec 256 butyl, 2-tert butyl, 2-sec amyl, 1,3-dimethyl, 2,3-dimethyl, 1,4-dimethyl, and 2,7-dimethyl, among others 257 (Porter, 1961). Following hydrogenation and removal of the metal catalyst, the hydroquinones are oxidized 258 back to quinones with oxygen (usually air) with simultaneous quantitative formation of hydrogen peroxide 259 (equation 3). Hydrogen peroxide is then extracted from the reaction mixture with water, and the quinones 260 are returned to the hydrogenator to complete another round of the catalytic cycle (Goor, 2007). Therefore, 261 AO processes lead to the net formation of hydrogen peroxide from gaseous hydrogen (H2) and molecular 262 oxygen (O2).

Fixed bed catalyst systems have also been developed for the AO process. This enhancement involves 264 incorporation of the transition metal catalyst into a fixed bed using a catalyst carrier/support (carbon, 265 magnesium carbonate, silicon carbide, aluminum oxide, etc.) in contrast to other industrial processes using 266 hydrogenation catalysts suspended within the reaction mixture. It generally involves a palladium catalyst and avoids the problem of filtration and recirculation of catalyst into the reaction between the 268 hydrogenation and oxidation steps of the AO process. In addition, fixed catalysts reduce contact time 269 between the reaction mixture and the hydrogenation catalyst, thereby minimizing undesired reduction 270 reactions within the anthraquinone molecule (Porter, 1961).

Solvent mixtures are almost always used to facilitate hydrogenation, oxidation and hydrogen peroxide 273 extraction in the AO process because quinones and hydroquinones have different solubilities. Quinones 274 dissolve readily in nonpolar, aromatic solvents (i.e., quinone solvents), while hydroquinones dissolve well 275 in polar solvents, such as alcohols and esters (i.e., hydroquinone solvents). It is also important for the 276 quinone and hydroquinone solvents to have low solubility in water and aqueous hydrogen peroxide 277 solutions, as well as sufficiently lower density than water to encourage separation of the two phases during 278 the extraction of hydrogen peroxide from the reaction mixture. Example quinone/hydroquinone solvent 279 mixtures that have been utilized in the AO process include polyalkylated benzenes with alkyl phosphates, 280 polyalkylated benzenes with tetraalkyl ureas, trimethylbenzenes with alkylcyclohexanol esters, and 281 methylnaphthalene with nonyl alcohols (Goor, 2007).

The aqueous hydrogen peroxide produced following the extraction with water is impure. The crude 283 product may be treated with polyethylene, activated carbon, ion exchangers or hydrocarbons to reduce the 284 amount of dissolved organic compounds in hydrogen peroxide solutions. Water-soluble organic 285 compounds are removed through oxidation (heating) followed by extraction with a suitable solvent (e.g., 286 the quinone solvent). The purified crude hydrogen peroxide product is then fed to a distillation unit where 287 it is purified further and concentrated to the usual commercial concentration of 50–70% by weight 288 hydrogen peroxide. Reverse osmosis membranes can also be used to purify crude, distilled or concentrated 289 (up to 70%) hydrogen peroxide (Goor, 2007).

Hydrogen peroxide can also be produced synthetically from compounds that contain the peroxy group; 291 from water and oxygen by thermal, photochemical, or electrochemical processes; and by the uncatalyzed 292 reaction of molecular oxygen with certain hydrogen-containing chemicals. Prior to industrialization of the 293 AO process, hydrogen peroxide was commercially produced using the reaction of barium peroxide or 294 sodium peroxide with an acid, the electrolysis of sulfuric acid and related compounds, and the 295 autoxidation of isopropyl alcohol (Eul, 2001; Goor, 2007). In addition, systems for the direct synthesis of 296 hydrogen peroxide from hydrogen (H2) and oxygen (O2) using finely dispersed catalysts have been 297 developed, and companies continue to patent systems based on this methodology (Reuter, 2006). However, 298 it is unlikely that any of these direct addition processes have achieved industrial-scale status (Goor, 2007).

Evaluation Question #3: Discuss whether the petitioned substance is formulated or manufactured by a 300 chemical process, or created by naturally occurring biological processes (7 U.S.C. § 6502 (21)).

According to USDA organic regulations, the NOP defines synthetic as “a substance that is formulated or 302 manufactured by a chemical process or by a process that chemically changes a substance extracted from 303 naturally occurring plant, animal, or mineral sources” (7 CFR 205.2). Hydrogen peroxide is a naturally 304 occurring inorganic compound; however, the sources of hydrogen peroxide used in commercial fungicides, 305 disinfectants and antiseptic products are produced through chemical synthesis. Indeed, industrial methods 306 for the preparation of hydrogen peroxide are categorized as oxidation-reduction reactions. Modern commercial methods for hydrogen peroxide synthesis involve the transition-metal catalyzed chemical 308 reduction of an alkyl anthraquinone with hydrogen (H2) gas to the corresponding hydroquinone followed 309 by regenerative oxidation of the latter species in air. We therefore conclude that hydrogen peroxide used 310 for plant disease control is a synthetic substance based on NOP definition and the use of synthetic chemical 311 reagents, catalysts and solvent in the production process. See the discussion in Evaluation Quesiton #2 for 312 details regarding the anthraquinone autoxidation (AO) method.

Evaluation Question #4: Describe the persistence or concentration of the petitioned substance and/or its 314 by-products in the environment (7 U.S.C. § 6518 (m) (2)).

Hydrogen peroxide is inherently unstable due to the weak peroxide (O–O) bond. At typical pesticide 316 concentrations, hydrogen peroxide is expected to degrade rapidly to water and oxygen (US EPA, 2007). 317 This section provides technical information on the fate, transport and persistence of hydrogen peroxide in 318 the terrestrial, aquatic and atmospheric compartments of the environment.

When used as a fungicide, hydrogen peroxide is likely to contact soils under a variety of environmental 320 conditions. Hydrogen peroxide degrades with an anaerobic (without oxygen) soil half-life of four hours in 321 soils containing petroleum (US EPA, 2007). It was also found that soil texture, pH and temperature had 322 little impact on the observed degradation rate. Under aerobic (with oxygen) soil conditions, dilute 323 solutions of hydrogen peroxide degrade with a half-life of 1.4 hours. These results were extrapolated to an 324 aerobic soil half-life of seven hours for concentrated solutions of hydrogen peroxide. Since the substance 325 has physical properties very similar to those of water, hydrogen peroxide is unlikely to preferentially bind 326 to soils when used in agricultural production (US EPA, 2007). Further, the calculated soil organic carbon-327 water partition coefficient (Koc) of 0.2 suggests that hydrogen peroxide will be highly mobile in soils. The 328 Henry’s Law constant for hydrogen peroxide indicates that volatilization of the substance from moist soils 329 and surface water is expected to be low (EC, 2003).

When released to water, hydrogen peroxide should be rapidly consumed through biodegradation and 331 photolysis. The half-life of hydrogen peroxide metabolism in water generally decreases with increasing size 332 of the microbial populations in the receiving water. Consequently, hydrogen peroxide degradation half-333 lives in natural waters range from a few hours to several days. Degradation in water is also catalyzed by 334 transition metals, including iron, copper, manganese, and chromium (Goor, 2007). In one study, 20% of the 335 applied hydrogen peroxide degraded (DT20) within 25–35 minutes in seawater. Hydrogen peroxide 336 degrades with a half-life of 1.1–5.3 hours under non-sterile aerobic aquatic conditions; however, the half-337 life increased to 80 hours under sterile aquatic conditions (US EPA, 2007). When microbial degradation is 338 possible, direct photolysis is unlikely to be the primary mechanism for aquatic decomposition of hydrogen 339 peroxide (Goor, 2007). Hydrogen peroxide is not expected to bioaccumulate in aquatic organisms due to its 340 low octanol-water partition coefficient (Kow) of 0.032 (US EPA, 2007).

Degradation of hydrogen peroxide released to the atmosphere is primarily a result of indirect photolysis 342 reactions with smaller contributions from direct photolysis and chemical reaction with organic substances. 343 Indirect photolysis is due to sensitization by secondary reactions with OH and O2 radicals and organic 344 substances. The most significant of these indirect degradation reactions is the reaction of hydrogen 345 peroxide with the hydroxyl (OH) radical. Direct hydrogen peroxide photolysis is initiated at wavelengths 346 of 280–380 nanometers (nm) with an estimated half-life of approximately two days. Light, oxygen, ozone, 347 hydrocarbons and free radicals in the atmosphere mediate hydrogen peroxide formation and release to the 348 atmosphere, likely at a significantly greater rate than the agricultural uses of the substance (Goor, 2007; Eul, 349 2001). Considering the various atmospheric degradation pathways, the overall tropospheric half-life of 350 hydrogen peroxide is estimated to be 10–24 hours (Goor, 2007; EC, 2003).

Evaluation Question #5: Describe the toxicity and mode of action of the substance and of its 352 breakdown products and any contaminants. Describe the persistence and areas of concentration in the 353 environment of the substance and its breakdown products (7 U.S.C. § 6518 (m) (2)).

Multiple EPA terrestrial effects characterizations have evaluated the toxicity of hydrogen peroxide and 355 other “peroxy compounds” to mammals and birds. Studies submitted by the registrants indicate that 356 hydrogen peroxide solutions used in pesticide products are corrosive to washed and unwashed eyes, as 357 well as exposed skin (i.e., Toxicity Category I for eye and skin irritation). The acute systemic toxicity of hydrogen peroxide products depends upon the formulation; specifically, products formulated as mixtures 359 of hydrogen peroxide and peroxyacetic acid are generally more toxic than those containing hydrogen 360 peroxide alone. Results of the acute toxicity studies indicate that formulated hydrogen peroxide products 361 are slightly to moderately toxic to rats (Toxicity Category II to III) via the oral, dermal and inhalation routes 362 of exposure, with lower levels of toxicity observed for hydrogen peroxide alone. In addition, the results of 363 a skin sensitization study suggest that hydrogen peroxide formulations are not likely to be a sensitizer in 364 mammals (US EPA, 1993; US EPA, 2009c). The product label for OxiDate (27% hydrogen peroxide) carries a 365 danger warning and the following precautionary statement (BioSafe, 2010):

Corrosive. Causes irreversible eye damage. May be fatal if swallowed or absorbed through the skin. Causes 367 skin burns or temporary discoloration on exposed skin. Do not breathe vapor. Do not get in eyes, on skin or 368 on clothing. Wear protective eyewear such as goggles or face shield. Wash thoroughly with soap and water 369 after handling. Remove and washing contaminated clothing before reuse.

Hydrogen peroxide is considered slightly toxic to practically non-toxic to birds on an acute oral basis. A 371 study of mallard ducks force-fed hydrogen peroxide via gavage administration provided a dose lethal to 372 50% of experimental birds (LD50) of 1,049 mg/kg, which indicates slight toxicity in birds. In addition, 373 dietary exposure studies in which Bobwhite quail were administered hydrogen peroxide in feed did not 374 result in significant mortality at any of the concentrations tested. No Observed Adverse Effect 375 Concentrations (NOAEC) in food of 47 and 1,953 part per million (ppm) were determined based on 376 unspecified adverse effects in the registrant submitted studies (US EPA, 2009c).

The substance has also been evaluated for systemic toxicity from chronic exposure, developmental and 378 reproductive toxicity, and carcinogenicity. According to the Agency for Toxic Substances and Disease 379 Registry (ATSDR), hydrogen peroxide is unlikely to cause chronic toxicity because hydrogen peroxide is 380 rapidly decomposed in mammalian bodies. However, repeat exposure to vapors of hydrogen peroxide 381 may cause chronic irritation of the respiratory tract and even partial or complete lung collapse (ATSDR, 382 2014). Laboratory exposure studies have not linked hydrogen peroxide exposure to adverse reproductive 383 and developmental effects. Chronic exposure studies in which hamsters were administered hydrogen 384 peroxide to their buccal cheek pouches (topical) five times per week for 20–24 weeks provided no evidence 385 of carcinogenicity. Adenomas and carcinomas of the duodenum were reported following oral 386 administration of hydrogen peroxide to mice in drinking water; however, the dermal exposure study in 387 mice indicated that hydrogen peroxide has no cancer promoting activity (IARC, 1999).

The in vitro mutagenicity of hydrogen peroxide is well established in the scientific literature. For example, 389 hydrogen peroxide induced DNA damage in several bacterial strains and mutation in Salmonella 390 typhimurium (Ames test) and Escherichia coli in the absence of exogenous metabolic activation. However, the 391 substance was not mutagenic in S. typhimurium in the presence of exogenous metabolic activation. Several 392 studies demonstrated that hydrogen peroxide causes gene mutation, sister chromatid exchanges, 393 chromosome aberrations and DNA single-strand breaks and fragmentations in mammalian cell lines, 394 including Chinese hamster cell cultures and human lymphocytes. In addition, tumor development was 395 observed in mice injected with mouse myeloid progenitor cells transformed through in vitro exposure to 396 hydrogen peroxide (IARC, 1999). A more recent in vitro study demonstrated that high concentrations of 397 hydrogen peroxide produced in the thyroid to oxidize iodide induces DNA double- and single-strand 398 breaks in rat, pig and human thyroid cell lines (Driessens, 2009).

Aquatic studies indicate that hydrogen peroxide is slightly toxic to aquatic invertebrates and practically 400 non-toxic to fish on an acute basis. Treatment of Daphnia magna (freshwater water flea) with 0.1, 1.0, 10 and 401 100 mg/L of a 35% hydrogen peroxide solution provided a 48-hour LC50 (concentration lethal to 50% of test 402 water fleas) of 24 mg/L and a NOAEC of 10 mg/L. Likewise, Bluegill sunfish and rainbow trout were 403 tolerant of hydrogen peroxide, with LC50 values and NOAECs ranging from 93–150 mg/L and 56–404 100 mg/L, respectively (US EPA, 2009c).

Evaluation Question #6: Describe any environmental contamination that could result from the 406 petitioned substance’s manufacture, use, misuse, or disposal (7 U.S.C. § 6518 (m) (3)).

Contamination is not expected when purified forms of hydrogen peroxide are released to the environment 408 following normal use. At typical pesticide concentrations, hydrogen peroxide is expected to rapidly degrade to oxygen gas and water (US EPA, 2007). Large-volume spills and other releases of concentrated 410 hydrogen peroxide could present a fire hazard since the substance readily decomposes to release oxygen 411 gas. Pure hydrogen peroxide is not flammable and can be diluted with clean water to minimize the risk of 412 fire (BioSafe, 2009). Although concentrated hydrogen peroxide is nonflammable, it is a powerful oxidizing 413 agent that may spontaneously combust on contact with organic material and becomes explosive when 414 heated (ATSDR, 2014; Eul, 2001). Combustion reactions and explosions resulting from accidental spills of 415 concentrated hydrogen peroxide could therefore lead to environmental degradation.

Moderate spills of hydrogen peroxide to marine and estuarine environments are unlikely to adversely 417 affect the receiving water bodies. On the contrary, a method describing the addition of hydrogen peroxide 418 to natural waters as an oxidizing agent for oil spill remediation was recently published in the patent 419 literature (Hoag, 2014). Likewise, hydrogen peroxide has been used to treat wastewater, and aids in the 420 removal of soil contaminants, including creosote, polycyclic aromatic hydrocarbons (PAHs), and other 421 inorganic and organic substances (Atagana, 2003; Conte, 2001; US EPA, 2007).

Toxic substances used in the manufacture of hydrogen peroxide, including alkyl anthraquinones, aromatic 423 solvents and transition metal catalysts (e.g., Raney nickel and palladium), are generally removed from 424 hydrogen peroxide prior to formulation of commercial pesticide products. Further, certain fractions of 425 these reagents, catalysts and solvents are often returned to the reactors for use in subsequent synthetic 426 reactions (Goor, 2007; Eul, 2001). Therefore, the chemicals used in the production of hydrogen peroxide 427 should not be released to the environment when manufacturers adhere to standard operating procedures 428 for safe handling and disposal of toxic substances.

Evaluation Question #7: Describe any known chemical interactions between the petitioned substance 430 and other substances used in organic crop or livestock production or handling. Describe any 431 environmental or human health effects from these chemical interactions (7 U.S.C. § 6518 (m) (1)).

Hydrogen peroxide reacts with oxidizable materials, including certain forms of the metals iron, copper, 433 brass, bronze, chromium, zinc, lead, manganese and silver. Contact of pure hydrogen peroxide with 434 organic materials may result in spontaneous combustion (ATSDR, 2014). Dilute hydrogen peroxide will 435 oxidize dry or moist organic substances, but concentrated hydrogen peroxide will react violently with 436 dried organic materials such as dehydrated compost or soil. Dilute and concentrated hydrogen peroxide 437 will oxidatively damage or destroy soil microorganisms (see Evaluation Question #8). In the well-known 438 Fenton reaction, iron cycles between the +2 and +3 oxidation states leading to the conversion of hydrogen 439 peroxide to reactive oxygen species, including the hydroxyl radical (US EPA, 2007). Because of their highly 440 reactive nature, these transient radical species are rapidly consumed through oxidative reactions with 441 organic materials or other processes that form water and oxygen gas as the byproducts. Further, hydrogen 442 peroxide does not deplete iron as part of the Fenton reaction and therefore should not adversely affect the 443 availability of this trace mineral in soils. Similar activation reactions are facilitated when hydrogen 444 peroxide is subjected to other naturally occurring transition metals (e.g, copper and chromium), as well as 445 iron-containing enzymes, such as catalase (US EPA, 2007).

Evaluation Question #8: Describe any effects of the petitioned substance on biological or chemical 447 interactions in the agro-ecosystem, including physiological effects on soil organisms (including the salt 448 index and solubility of the soil), crops, and livestock (7 U.S.C. § 6518 (m) (5)).

Non-target soil organisms may be damaged or destroyed following application of hydrogen peroxide 450 fungicides to plants and soils. Currently registered hydrogen peroxide products are labeled as algicides, 451 antifoulants, bacteriocides/bacteriostats, disinfectants, fungicides/fungistats, nematicides, 452 microbiocides/microbiostats, molluscicides, sporicides, sanitizers, sterilizers, tuberculocides and virucides 453 (BioSafe, 2010). For example, the downy mildew fungal organisms Pseudoperonospora cubensis and the pink 454 rot of potato fungus Phytophthora erythroseptica are susceptible to the oxidizing effects of hydrogen peroxide 455 (Kuepper, 2003; Al-Mughrabi, 2006). It therefore follows that populations of beneficial soil fungi, such as 456 Mycorrhizal fungi, and nitrogen-fixing bacteria may be negatively impacted by large-scale soil treatments of 457 fungicides containing hydrogen peroxide. Other soil organisms, including nematodes, earthworms, snails 458 and grubs are also at risk depending on the concentration and volume of hydrogen peroxide applied to 459 soil. Indeed, recent studies demonstrated that soil drenches of dilute hydrogen peroxide adversely impact 460 reproduction in the root-knot nematode Meloidogyne javanica (Karajeh, 2008), suggesting that similar treatments may impact populations of beneficial soil nematode species. The effects of hydrogen peroxide 462 fungicides on beneficial soil organisms should be manageable at the population level since the substance 463 degrades rapidly to water and oxygen in the environment and provides no residual activity.

Direct application or drift of concentrated hydrogen peroxide foliar sprays to treatment and non-target 465 plants may result in phytotoxicity. The OxiDate product label states that use of solutions more 466 concentrated than prescribed may result in leaf necrosis (cell death) in some plants. Applicators are 467 advised to use 1:100 dilutions of the Oxidate product; since the concentrate is 27% hydrogen peroxide, this 468 dilution ratio provides a working spray solution consisting of approximately 0.3% hydrogen peroxide 469 (BioSafe, 2010). While plant damage is not expect at label application rates, plant sensitivity to hydrogen 470 peroxide solutions should be assessed before applying the substance to a large area.

Overall, the available information suggests that large volumes of concentrated hydrogen peroxide 472 solutions will adversely affect the viability and reproduction of non-target microorganisms, including 473 beneficial soil fungi and nematodes. Information was not identified on the potential or actual impacts of 474 hydrogen peroxide upon endangered species, populations, viability or reproduction and the potential for 475 measurable reductions in genetic, species or eco-system biodiversity.

Evaluation Question #9: Discuss and summarize findings on whether the use of the petitioned 477 substance may be harmful to the environment (7 U.S.C. § 6517 (c) (1) (A) (i) and 7 U.S.C. § 6517 (c) (2) (A) 478 (i)).

Hydrogen peroxide is an unstable inorganic compound and is expected to degrade rapidly to water and 480 oxygen in the environment. The half-lives for aerobic and anaerobic degradation of hydrogen peroxide in 481 various soils are between one and seven hours. Hydrogen peroxide is mobile in soils, but does not readily 482 volatilize from moist soils and surface waters (EC, 2003; US EPA, 2007). When released to water, hydrogen 483 peroxide is rapidly consumed through biodegradation and photolysis. The half-life for biodegradation of 484 hydrogen peroxide in water generally ranges from minutes to several hours (Goor, 2007; US EPA, 2007). 485 Light, oxygen, ozone, hydrocarbons and free radicals contribute to hydrogen peroxide formation in the 486 atmosphere, likely at significantly greater rates than the agricultural uses of the substance. The overall 487 tropospheric half-life of hydrogen peroxide is estimated to be 10–24 hours (EC, 2003; Eul, 2001; Goor, 2007). 488 Under typical use conditions, diluted and pure forms of hydrogen peroxide are reactive with transition 489 metals (e.g., iron, copper, chromium) and organic materials (US EPA, 2007; ATSDR, 2014).

Ecological receptors are insensitive to moderately sensitive to hydrogen peroxide solutions. Hydrogen 491 peroxide is considered slightly toxic to practically non-toxic to birds on an acute oral basis. Likewise, 492 aquatic toxicity studies indicate that hydrogen peroxide is slightly toxic to aquatic invertebrates and 493 practically non-toxic to fish on an acute exposure basis. In contrast to birds and aquatic animals, 494 microorganisms are particularly sensitive to various concentrations of hydrogen peroxide. The scientific 495 literature and agricultural experience have demonstrated that hydrogen peroxide is toxic to pathogen soil 496 organisms, such as the downy mildew fungus Pseudoperonospora cubensis and pink rot of potato fungus 497 Phytophthora erythroseptica (Kuepper, 2003; Al-Mughrabi, 2006). Considering the oxidizing mode of action 498 for hydrogen peroxide, it is likely that the substance is also toxic to beneficial soil organisms, including 499 Mycorrhizal fungi and nitrogen-fixing bacteria. This non-target effect is most relevant for spray drift and 500 soil drench scenarios, and should not present a population-level concern for controlled hydrogen peroxide 501 applications.

Environmental contamination is not expected when purified forms of hydrogen peroxide are released to 503 the environment. At typical pesticide concentrations, hydrogen peroxide is expected to rapidly degrade to 504 oxygen gas and water (US EPA, 2007). The toxic solvents and reagents used in the manufacture of 505 hydrogen peroxide are removed prior to product formulation and, in many cases, are reused in subsequent 506 synthetic reactions (Eul, 2001; Goor, 2007). As such, it is unlikely that these chemicals are readily 507 introduced into the environment as a result of hydrogen peroxide production.

Evaluation Question #10: Describe and summarize any reported effects upon human health from use of 509 the petitioned substance (7 U.S.C. § 6517 (c) (1) (A) (i), 7 U.S.C. § 6517 (c) (2) (A) (i)) and 7 U.S.C. § 6518 510 (m) (4)).

Hydrogen peroxide is generally considered safe for human exposure at low doses. Indeed, the US Food 512 and Drug Administration (FDA) affirmed hydrogen peroxide as Generally Recognized as Safe (GRAS) 513 when used as a direct food additive with certain limitations (see “Approved Legal Uses of the Substance” 514 for details). Acute irritation and systemic toxicity is possible in humans exposed to moderate to high doses 515 of hydrogen peroxide. Systemic effects of the substance generally result from the release of oxygen gas and 516 water as the enzyme catalase decomposes available hydrogen peroxide. Specifically, venous embolism (gas 517 bubble in bloodstream) may occur when the amount of oxygen gas produced exceeds its blood solubility 518 (ATSDR, 2014).

Ingestion of household solutions (3%) typically causes mild gastrointestinal irritation and vomiting. Gastric 520 distension (bloating of the stomach) may occur due to liberation of oxygen, but hollow-organ (e.g., 521 stomach) rupture is unlikely when dilute solutions are ingested. In contrast, the ingestion of concentrated 522 solutions (≥ 10%) can cause extreme irritation, inflammation, burns of the alimentary tract, and hollow-523 organ distension and rupture. Vapors, mists or aerosols of hydrogen peroxide can cause upper airway 524 irritation, inflammation of the nose, hoarseness, shortness of breath, and tightness or a burning sensation in 525 the chest. Inhalation or ingestion of hydrogen peroxide at high concentrations may lead to seizures, 526 cerebral embolism or even tissue death (infarction). Dermal exposure to dilute hydrogen peroxide 527 solutions can irritation and temporary bleaching of the skin, whereas concentrated solutions can cause 528 severe skin burns with blistering. In addition, contact of dilute hydrogen peroxide solutions with the eyes 529 can cause stinging pain and tearing, while solutions that are 5% or greater can cause injury to the eye 530 surface (ATSDR, 2014). 531

The most recent US EPA Human Health Scoping Document for peroxy compounds provides a summary of 532 incidents and associated symptoms associated with hydrogen peroxide exposure. As of the 2009 review, a 533 total of 98 individual human incidents were submitted to the Agency, which summarized the symptoms 534 observed in those cases as follows (US EPA, 2009d):

The most common symptoms reported were acute symptoms based on acute corrosion and irritation effects. 536 The symptoms include eye irritation, skin burns, esophageal burns, nausea, dizziness, rash, and headaches. 537 Inhalation effects include chest congestion, respiratory irritation, coughing of blood, tightness of chest and 538 shortness of breath. Dermal effects include edema, erythema, skin burns, blistering, and swelling. These cases 539 led to hospitalization in some cases.

Hydrogen peroxide is unlikely to cause chronic toxicity in humans because it is rapidly decomposed in the 541 body. The available toxicity and epidemiology studies provide no evidence of reproductive or 542 developmental toxicity in experimental animals and humans (ATSDR, 2014). Although oral administration 543 of hydrogen peroxide resulted in the formation of adenomas and carcinomas in mice, carcinogenic effects 544 were not observed in topical application studies using mice and hamsters. Further, a 1991 case-control 545 study found no association between hydrogen peroxide exposure in hairdressers, textile bleachers and 546 furriers and the occurrence of several types of cancer, including esophageal, stomach, colon, rectum, 547 pancreatic, lung, prostate, bladder, and kidney cancer, as well as skin melanoma and lymphoma (IARC, 548 1999). On the other hand, hydrogen peroxide is a known mutagen and is associated with genotoxicity in 549 mammalian and human cell lines (IARC, 1999; Driessens, 2009). IARC determined that there is inadequate 550 evidence in humans and limited evidence in experimental animals for the carcinogenicity of hydrogen 551 peroxide, classifying the substance as Group 3 – Not classifiable as to its carcinogenicity to humans (IARC, 552 2014).

Evaluation Question #11: Describe all natural (non-synthetic) substances or products which may be 554 used in place of a petitioned substance (7 U.S.C. § 6517 (c) (1) (A) (ii)). Provide a list of allowed 555 substances that may be used in place of the petitioned substance (7 U.S.C. § 6518 (m) (6)).

Numerous alternatives exist for hydrogen peroxide solutions used as disinfectants, sanitizers and algicides 557 on crop production tools and equipment, as well as plant disease control agents (fungicides) in the organic 558 production of crop commodities. This section provides a summary of available naturally occurring and 559 synthetically produced substances that may serve as alternatives for hydrogen peroxide according to the 560 use patterns under sunset review with the National Organic Standards Board.

Alternative Algicides, Disinfectants and Sanitizers

Technical information regarding the efficacy of natural, nonsynthetic agricultural commodities or products 563 that could substitute for hydrogen peroxide as a sanitizer in organic crop production is limited. 564 Nonsynthetic (natural) sources of ethanol may substitute for hydrogen peroxide disinfectants. Certain 565 essential oils exhibit antiviral and antibacterial properties, and are commonly used in homemade hand 566 sanitizers. Examples of the strongest and most commonly used antiseptic essential oils include clove oil, 567 melaleuca oil, and oregano oil. In addition, pine oil, basil oil, cinnamon oil, eucalyptus oil, helichrysum oil, 568 lemon and lime oils, peppermint oil, tea tree oil, and thyme oil are also used as antiseptic substances. Aloe 569 vera contains six antispectic agents (lupeol, salicylic acid, urea nitrogen cinnamonic acid, phenols and 570 sulfur) with inhibitory action on fungi, bacteria and viruses (Surjushe, 2008). Depending on the required 571 potency and intended application, essential oils may be used in pure form or as a mixture in carrier, such 572 as water. University agricultural extension literature databases contained no articles related to the practice 573 of using essential oils as disinfectants or any performance data for these oils relative to hydrogen peroxide. 574 It is therefore uncertain whether essential oil mixtures could serve as viable, naturally derived alternatives 575 to hydrogen peroxide for the disinfection of tools and equipment used in organic crop production.

A wide variety of synthetic substances are available for sanitizing and disinfecting the surfaces of cutting 577 tools and other implements in crop production. Laboratory experiments have evaluated the efficacy of 578 Clorox (sodium hypochlorite (NaClO; 7 CFR 205.601(a)(2)(iii)), Lysol (soap, o-phenylphenol, o-benzyl-p-579 chlorophenol, ethanol, xylenols, isopropanol, tetrasodium ethylenediamine tetraacetate), Pine-Sol (pine 580 oil), rubbing alcohol (isopropanol), Lysterine (thymol, eucalytol, methyl salicylate, menthol, ethanol, 581 benzoic acid, poloxamer 407), hydrogen peroxide (H2O2; 7 CFR 205.601(a)(4)), Agrimycin 17 (streptomycin 582 sulfate), and Kocide 101 (cupric hydroxide and metallic copper) for preventing the transmission of fire 583 blight bacteria in ‘Granny Smith’ apple and ‘Shinseiki’ Asian pear fruit (Teviotdale, 1991). The combined 584 results indicate that spray and 3–5 minute soaking treatments of Clorox, Lysol, and Pine-Sol were superior 585 to corresponding treatments of the other products as well as dip treatments of all commercial disinfectants. 586 In addition, quaternary ammonium chloride salts, chlorine dioxide (ClO2; 7 CFR 205.601(a)(2)(ii)) and 587 sodium carbonate peroxyhydrate (7 CFR 205.601(a)(8)—which produces hydrogen peroxide (H2O2) and 588 sodium carbonate (Na2CO3) when dissolved in water—have been used as effective algicides, bactericides, 589 virucides, and fungicides for greenhouse surface disinfection (Benner, 2012).

In addition to hydrogen peroxide (7 CFR 205.601(a)(4)), the National List of Allowed and Prohibited 591 Substances permits the use of the following synthetic materials as algicides, disinfectants, and sanitizers, 592 including irrigation system cleaning, in organic crop production:

• Ethanol. Molecular formula of CH3CH2OH; allowed according to the listing for alcohols (7 CFR 594 205.601(a)(1)(i)).
• Isopropanol. Molecular formula of (CH3)2CHOH; allowed according to the listing for alcohols (7 596 CFR 205.601(a)(1)(ii)).
• Calcium hypochlorite. Molecular formula of Ca(ClO)2; allowed according to the listing for 598 chlorine-based materials (7 CFR 205.601(a)(2)(i)).
• Chlorine dioxide. Molecular formula of ClO2; allowed according to the listing for chlorine-based 600 materials (7 CFR 205.601(a)(2)(ii)).
• Sodium hypochlorite. Molecular formula of NaClO; allowed according to the listing for chlorine-602 based materials (7 CFR 205.601(a)(2)(iii)).
• Copper sulfate. Molecular formula of CuSO4. Allowed for use as an algicide in aquatic rice 604 systems; limited to one application per field during any 24-month period (7 CFR 205.601(a)(3)).
• Ozone gas. Molecular formula of O3. Allowed for use only as an irrigation system cleaner (7 CFR 606 205.601(a)(5)).
• Peracetic acid. Molecular formula of CH3CO3H. Allowed for use in disinfecting equipment, seed, 608 and asexually propagated plant material. Also permitted in hydrogen peroxide formulations as 609 allowed in §205.601(a) at concentration of no more than 6% as indicated on the pesticide product 610 label (7 CFR 205.601(a)(6)).
• Soap-based algicide/demossers. Consist of mixtures of ammonium or potassium salts of fatty 612 acids with varying molecular weight components; allowed according to 7 CFR 205.601(a)(7).
• Sodium carbonate peroxyhydrate. Molecular formula of 2 Na2CO3 • 3 H2O2. Allowed for use 614 according to 7 CFR 205.601(a)(8); federal law restricts the use of this substance in food crop 615 production to approved food uses identified on the product label.

Alternative Plant Disease Control Agents

A number of naturally occurring, non-synthetic substances exist for the control and prevention of 618 pathogenic microorganisms that cause plant diseases. Natural sources of elemental sulfur have been used 619 to manage grapevine powdery mildew for almost 200 years (Vasquez, 2009); however, the sulfur used in 620 modern formulated products is likely produced synthetically from fossil fuels (Nehb & Vydra, 2006). 621 Sulfur operates through a multi-site mode of action involving inhibition of fungal spore germination and 622 production of toxic vapors that impair cellular respiration in target organisms (Vasquez, 2009). Other 623 natural active ingredients used to manage plant diseases in organically grown crops include botanical oils, 624 plant extracts and microorganisms.

Natural products and horticultural oils derived from plant sources are commonly used to combat and 626 prevent the development of plant pathogens. Neem oil containing the active ingredients azadirachtin and 627 salannin is a botanical fungicide, insecticide and miticide derived from the neem tree (Pottorff, 2010). 628 Commercially available neem oil products, such as the OMRI-listed product Neem Oil 70% manufactured 629 by Certis USA, are used to control anthracnose, scab and leaf blight, as well as aphids, psyllids, mealybugs, 630 leafhoppers and scale insects on a variety of crops and ornamentals (Certis USA, 2014). Natural plant oils, 631 including oil of thyme, sesame, clove and rosemary, and extract of Reynoutria sachalinensis (Giant 632 Knotweed) have also been used as active ingredients in OMRI-approved fungicides, insecticides and 633 miticides (McGrath, 2010). Lastly, it has been noted that foliar sprays of compost tea are successful in 634 managing a number of plant diseases (Kuepper, 2003). Horticultural oils produced synthetically are 635 included on the National List for organic crop production (see list below).

Certain bacterial and fungal strains are used as active ingredients in commercially available fungicide 637 products. Beneficial microorganisms provide control of plant diseases through various modes of action: (1) 638 outcompeting the pathogen for nutrients and space, (2) producing a chemical compound that acts against 639 the pathogen, (3) directly attacking the pathogen, and/or (4) triggering a defensive response in the host 640 plant that limits the invading ability of the pathogen (Swain, 2014). For example, the gram-positive 641 bacterium Bacillus subtilis is used as the active ingredient in several biological fungicides, including the 642 Serenade® products manufactured by Bayer CropScience, by producing proteins that inhibit spore 643 germination in fungi that cause powdery mildew and other plant diseases (Vasquez, 2009). Likewise, the 644 gram-negative bacterium Pseudomonas fluorescens (FrostbanTM by Nufarm Americas, Inc) is used as a foliar 645 spray to compete with fire blight bacterium for nutrients in apple and pear tree blossoms. Biofungicides 646 work best when applied preventatively (Swain, 2014).

In addition to naturally occurring materials, several synthetic substances are also permitted for use as plant 648 disease control agent in organic crop production:

• Elemental sulfur. In addition to natural sources, synthetic elemental sulfur (i.e., derived from 650 petroleum materials) is approved for use in organic crop production as an insecticide (7 CFR 651 205.601(e)(5)) and for plant disease control (7 CFR 205.601(i)(10) without restrictions.
• Horticultural oils. Narrow range oils, such as dormant, suffocating and summer oils may be used 653 for plant disease control in organic crop production (7 CFR 205.601(i)(7)). In addition, synthetic oils 654 are allowed for use as insecticides (7 CFR 205.601(e)(8)).
• Aqueous potassium silicate (CAS # 1312-76-1). According to the final rule, the silica used in the 656 manufacture of potassium silicate must be sourced from naturally occurring sand when used in 657 organic crop production for plant disease control (7 CFR 205.601(i)(1)) and for insecticidal and 658 miticidal purposes (7 CFR 205.601(e)(2)).
• Copper sulfate. The synthetic substance may be used for plant disease control in a manner that 660 minimizes accumulation of copper in soil (7 CFR 205.601(i)(3)). As an insecticide, only allowed for 661 use as tadpole shrimp control in aquatic rice production. Treatments are limited to one application 662 per field during any 24-month period. Application rates are limited to levels which do not increase baseline soil test values for copper over a timeframe agreed upon by the producer and accredited 664 certifying agent (7 CFR 205.601(e)(4)).
• Coppers, fixed. Copper hydroxide, copper oxide, copper oxychloride (includes products exempted 666 from EPA tolerance) may be used for plant disease control provided that copper-based materials 667 are used in a manner that minimizes accumulation in the soil and shall not be used as herbicides (7 668 CFR 205.601(i)(2)).
• Hydrated Lime. The reaction of lime with water produces synthetic hydrated or “slaked” lime 670 (calcium hydroxide). Hydrated lime is allowed for use as a plant disease control agent in organic 671 crop production (7 CFR 205.601(i)(5)).
• Lime Sulfur. Consists of a mixture of elemental sulfur and hydrated lime (calcium hydroxide). The 673 synthetic substance is permitted for use as a plant disease control agent in organic crop production 674 (7 CFR 205.601(i)(6)). In particular, lime sulfur is commonly used to control pathogenic organisms 675 in organic apple and grape production.
• Peracetic acid. Used to control fire blight bacteria. Also permitted in hydrogen peroxide 677 formulations as allowed in §205.601(i) at a concentration of no more than 6% as indicated on the 678 pesticide product label (7 CFR 205.601(i)(8)).
• Potassium bicarbonate. The synthetic substance is allowed for use as a plant disease control agent 680 in organic crop production (7 CFR 205.601(i)(9)).

Evaluation Question #12: Describe any alternative practices that would make the use of the petitioned 682 substance unnecessary (7 U.S.C. § 6518 (m) (6)).

Proper implementation of crop rotation and incorporation of cover crops can effectively minimize the 684 occurrence of plant diseases and corresponding applications of chemical fungicides. Crop rotations are 685 critical for reducing the adverse impacts plant pathogens, pest insects and weeds on various crop varieties. 686 By changing environmental conditions in the field and removing food sources to prevent pest buildup, 687 crop rotations have enabled organic and conventional farmers to reduce pest populations (McGuire, 2003). 688 Crops of the same family should not follow one another in the field, and should typically be separated by 689 at least two years and as much as five years to minimize the occurrence of pests and pathogens in the soil 690 (Baldwin, 2006). A rotation of crop families might include Brassicaceae (cole crops), followed by Asteraceae 691 (lettuce, cut flowers), followed by Solanaceae (tomatoes, potatoes, peppers, eggplants), followed by 692 Curbitaceae (squashes, cucumbers and melons). Specific plant diseases will require tailored crop rotations; 693 for example, detection of Sclerotium rolfsii (southern blight) in vegetable crops may require a rotation of 694 corn, grass, hay or pasture crop for two or three years (Baldwin, 2006).

Planting cover crops for biological fumigation has the potential to curtail the use of chemical fungicides 696 during the growing season by reducing the populations of soil borne pathogens prior to planting. Certain 697 varieties of mustard cover crops (e.g., Ida Gold, Mighty Mustard and Pacific Gold) planted in a resting field 698 are grown for a certain period of time and then plowed under before reaching full maturity in order to 699 maximize the concentration of nutrients and allelochemicals available from the mustard crop (Johnson, 700 2009). Specifically, damaged plant tissues of mustard plants naturally release the biofumigant allyl 701 isothiocyanate. Green manures from various cover crops may also serve as energy sources for beneficial 702 microorganisms that out-compete plant pathogens and potentially confer disease resistance to crops 703 (McGuire, 2003).

Crop rotation and the incorporation of cover crops are commonly employed methods of controlling soil-705 borne pests and pathogens in annual cropping systems. However, these methods are incompatible with the 706 growing requirements of perennial fruit trees, grape vines and bushes (e.g., raspberries and blackberries) 707 typically treated with hydrogen peroxide to prevent and control diseases caused by various plant 708 pathogens. Despite these limitations, several alternative strategies have been developed to minimize the 709 use of chemical fungicides on perennial crops.

Providing effective control of plant diseases on tree crops and ornamentals requires an integrated 711 approach. Starting with certified and disease-free plant material will allow for faster growth and 712 heightened resistance to environmental stressors and less susceptibility to fungal pathogens (Holb, 2009). 713 Using apple scab control as an example, sanitation practices such as picking up and disposing of fallen 714 leaves in the fall can be effective for smaller operations but is not always practical for large orchards. In conventional production, urea can be applied to apple trees just before leaves drop or directly to leaves on 716 the ground followed by tilling the fallen leaves into the soil or chopping them into small pieces to 717 accelerate leaf decomposition. This practice significantly decreases the amount of apple scab pathogen 718 available the next growing season (Vaillancourt, 2005). Although similar mechanical strategies can be 719 employed in organic orchards, urea—a synthetic nitrogen fertilizer—is not approved for use in organic 720 crop production. Flaming using a torch-directed flame sears the leaf litter on the orchard floor and ruptures 721 fungal cells on the affected leaves (Holb, 2009). Regular pruning of apple trees enables direct management 722 of several fungal diseases through removal of diseased shoots, fruit, stems or dead wood that can harbor 723 pathogens (Holb, 2009). Pruning also enhances air movement and the penetration of sunlight within the 724 canopy, thus hastening the drying process for leaves and fruit. Likewise, it is generally recommended that 725 growers avoid overhead irrigation, especially when weather conditions are favorable for apple scab 726 development. Both of the latter two strategies minimize the occurrence of moist conditions that support 727 fungal infections (Vaillancourt, 2005; Holb, 2009).

Physical methods are also available for postharvest control of pathogens on raw agricultural commodities. 729 Using table grapes as an example, ultraviolet light at wavelengths between 200–280 nanometers (UV-C) as 730 well as temperature and pressure changes are viable options for controlling various mold species. For 731 example, UV-C treatment at 254 nm effectively controlled gray mold, which was reduced from 22 and 52% 732 in control to 14 and 38% in grapes. Laboratory scale applications of hyperbaric pressures such as 733 1140 mmHg (1.5 atm) successfully decreased the percentage of infected berries and lesion diameter of gray 734 mold on artificially inoculated berries. The authors note that antimicrobial treatments involving pressures 735 higher than atmospheric require additional study in large-scale tests before the widespread deployment of 736 this method in agricultural production (Romanazzi, 2012). Postharvest heat treatments such as hot water 737 treatment, short hot water rinsing and brushing, and hot air treatment may reduce rot development and 738 enhance fruit resistance to chilling injury in cold-sensitive cultivars. However, it is noted that complete 739 control of decay is rarely achieved using heat therapy alone (Schirra, 2011).

The cultural practices summarized above may minimize but are unlikely to eliminate the need for natural 741 or synthetic pesticides during periods of intense disease pressure. Alternatives substances to hydrogen 742 peroxide for plant disease control are summarized in Evaluation Question #11.