Formal Recommendation 

From: National Organic Standards Board (NOSB)

To: the National Organic Program (NOP)

Date: April 26, 2019

Subject: Silver dihydrogen citrate

NOSB Chair: Harriet Behar

The NOSB hereby recommends to the NOP the following:

Rulemaking Action: None

Statement of the Recommendation: 

The NOSB does not recommend listing of Silver Dihydrogen Citrate as an antimicrobial 

processing aid for poultry carcasses and fruits and vegetables and as a disinfectant/sanitizer for 

food contact surfaces and food processing equipment on the National List at 7 CFR 205.605(b) 

as a synthetic nonagricultural (nonorganic) substance allowed in or on processed products 

labeled as “organic” or“ made with organic (specified ingredients).”

Rationale Supporting Recommendation (including consistency with OFPA and Organic 

Regulations): 

The NOSB finds merit for this material, particularly around the need for alternative sanitizers in 

organic processing. However, concerns remain about its potential impact on the environment 

(persistence, bioaccumulation), compatibility with organic production given concerns about 

nano-particles, the use of sodium lauryl sulfate in the formulation, it’s presences as an 

unlabeled substance on processed organic products, potential effects on the efficacy of silver in 

medical settings, and wastewater treatment during early processing on farms without sewerage 

connections. 

NOSB Vote: 

Classification Motion: 

Motion to classify silver dihydrogen citrate as synthetic 

Motion by: Tom Chapman 

Seconded by: Lisa de Lima 

Yes: 14 No: 0 Abstain: 0 Absent: 0 Recuse: 0

Listing Motion: 

Motion to add silver dihydrogen citrate at §205.605(b) 

Motion by: Tom Chapman 

Seconded by: Lisa de Lima 

Yes: 0 No: 13 Abstain: 1 Absent: 0 Recuse: 0 

Motion Failed
National Organic Standards Board

Handling Subcommittee Petitioned Material Proposal

Silver Dihydrogen Citrate

February 5, 2019

Summary of Petition:

Silver Dihydrogen Citrate it being petitioned by Pure Bioscience, Inc. as an antimicrobial processing aid 

for poultry carcasses and fruits and vegetables (excluding citrus and grapes for winemaking) and as a 

disinfectant/sanitizer for food contact surfaces and food processing equipment (Petition pg. 1, TR 31-34, 

127-132). As such it is being petitioned to be listed on the National List at 7 CFR 205.605(b), synthetic 

nonagricultural (nonorganic) substance allowed in or on processed products labeled as “organic” or 

“made with organic (specified ingredients).” The petition was received on 1/18/2017 (referred to as 

“petition”) and amended on 8/1/17 and 6/29/18 (referred to as “addenda”). A Technical Review (TR) 

was completed and found sufficient on 5/15/2018 (referred to as “TR”). The NOSB considered the 

petition at its Fall 2018 meeting but voted to send it back to subcommittee for further review after 

receiving substantial public comment. The NOSB is bringing this forward again for full Board review at its 

Spring 2019 meeting.

Summary of Review:

Based on the information provided in the TR and by the petitioner, SDC appears to be of low risk to the 

environment and to human health both in its use and disposal. However, public comments received as 

part of the Fall 2018 NOSB meeting disputed some of these assertations. Several groups cited research 

documenting microbial resistance to silver ions as well as that silver- and antibiotic-resistant genes are 

frequently transmitted together. Public comments at the Fall 2018 NOSB meeting quoted data that SDC 

is of low risk to the environment if it is disposed of through a managed water treatment system. 

However, disposal through other treatment systems, such as septic systems, could be problematic. One 

commenter cited the EPA registration for Silver dihydrogen citrate which states, “Do not discharge 

effluent containing this product into lakes, streams, ponds, estuaries, oceans or other waters... do not 

discharge effluent containing this product to sewer systems without previously notifying the local 

sewage treatment plant authority.” If approved, SDC could be used by all types of

handling and postharvest handling operations, including those that are not connected to

municipal waste water systems and do not have an on-site wastewater treatment facility.

Examples of such uses are activities that commonly occur on-farm or at consolidation points

located in rural areas: hydro-cooling, washing, flotation, sorting, packing, etc. The Subcommittee still 

has concerns around the use of this material in potential field applications - this could potentially be 

mitigated by an annotation disallowing its use based on the available wastewater treatment facilities for 

the effluent. 

Alternative materials, natural and synthetic, are available; however, these substances have limited 

applications or utilize a similar oxidative mode of action. There is a growing concern about the 

development of bacterial resistance to oxidative antibacterial agents. Several industry comments were 

received for the Fall 2018 NOSB meeting asserting that this material would be useful as part of a 

pathogen risk reduction strategy. Other commenters were concerned that approving the use of silver 

ions in organic production could lead to pathogen resistance in humans and reduce the effectiveness of 

a human medical treatment, similar to the argument against antibiotic use in organic agriculture. 

However, this is also a concern relevant to most sanitizers included on the national list, including 

chlorhexidine and chlorine compounds (which have been shown to in some studies accelerate antibiotic 
resistant bacteria). The Subcommittee did not find the use of this material in medical applications as 

violative of the OFPA criteria. 

The NOSB has received public comment from interest groups that are concerned that the inclusion of 

SDC will allow the use of nano-silver and that nano-silver is necessary for the sanitizing efficacy of this 

substance. The petitioner denies nano-silver is a part of this formulation and the technical report speaks 

to the efficacy of this substance without nano-silver. An annotation was included in the Fall 2018 NOSB 

proposal to limit particle sizes to greater than 300nm. However, the petitioner provided comments that 

the silver occurs in ionic form and thus cannot be categorized as a particle size and that this annotation 

is not pertinent to this product. The Subcommittee has unresolved concerns about whether or not this 

substance meets the previous NOSB recommendations on nano-particles and therefore the 

Subcommittee questions if this material is compatible with a system of organic production. 

There is conflicting information about the use of sodium lauryl sulfate in this substance. The petitioner 

claims the sodium lauryl sulfate is used as a stabilizer. However, a public commenter cited the patent 

documents that look at the use of sodium lauryl sulfate as a detergent to increase efficacy. If sodium 

lauryl sulfate is used as a detergent in a no-rinse application this substance should also be petitioned 

separately to the national list. 

The NOSB finds merits for this material, particularly around the need for alternative sanitizers in organic 

processing and its relative minimal potential human health impacts. However, concerns linger around 

its potential impact on the environment, its compatibility with organic production given the concerns 

around nano-particles and concerns around the use of sodium lauryl sulfate in formulation. At this time 

the Subcommittee is not recommending this material for inclusion on the National List. If the noted 

concerns above can be mitigated or addressed, then the above material could be re-petitioned for 

reconsideration. 

Category 1: Classification 

1. Substance is for: ____X___ Handling _______ Livestock

2. For HANDLING and LIVESTOCK use:

a. Is the substance Agricultural or ____X___ Non-Agricultural?

 Describe reasoning for this decision using NOP 5033-2 as a guide:

“Silver dihydrogen citrate is a synthetic material solely manufactured by a chemical process, not 

extracted from naturally occurring plant, animal, or mineral sources. Silver dihydrogen citrate is 

produced electrolytically, through the immersion of silver electrodes in an aqueous solution of citric 

acid. “ (TR 240-242).

b. If the substance is Non-agricultural, is the substance __ Non-synthetic or _X_ Synthetic? 

Is the substance formulated or manufactured by a process that chemically changes a 

substance extracted from naturally occurring plant, animal, or mineral sources? [OFPA 

§6502(21)] If so, describe, using NOP 5033-1 as a guide: 

“Silver dihydrogen citrate is a synthetic material solely manufactured by a chemical process, not 

extracted from naturally occurring plant, animal, or mineral sources. Silver dihydrogen citrate is 
produced electrolytically, through the immersion of silver electrodes in an aqueous solution of citric 

acid. “ (TR 240-242)

3. For LIVESTOCK: Reference to appropriate OFPA category

Is the substance used in production, and does it contain an active synthetic ingredient in the 

following categories: [§6517(c)(1)(B)(i)]; copper and sulfur compounds; toxins derived from 

bacteria; pheromones, soaps, horticultural oils, fish emulsions, treated seed, vitamins and 

minerals; livestock parasiticides and medicines and production aids including netting, tree wraps 

and seals, insect traps, sticky barriers, row covers, and equipment cleansers; or (ii) is used in 

production and contains synthetic inert ingredients that are not classified by the Administrator 

of the Environmental Protection Agency as inerts of toxicological concern?

Not Applicable

Category 2: Adverse Impacts 

1. What is the potential for the substance to have detrimental chemical interactions with other 

materials used in organic farming systems? [§6518(m)(1)]

“SDC is incompatible with aluminum sulfate, aluminum ammonium chloride, aluminum 

orthophosphate, chlorides, sequestering agents designed to remove transition metals from 

solution, EDTA (above 1.5%), and calcium hardness above 300 ppm. These substances are not 

on the National List. The product is compatible with most metals including stainless steels. 

Ionic silver rapidly reacts with chlorides and some other anions that will result in low solubility 

silver salts. This reaction would potentially affect stability of the product. We recognize that 

two chloride salts, calcium and potassium, are permitted for use in organic processing, but the 

chloride salts are not expected to be used during the early processing stages. Therefore, the 

silver dihydrogen citrate would not be anticipated to have the opportunity to react with those 

substances and adversely impact the stability of the product.” (Petition page 4) and (TR 100-

103). This product is intended for processing use and not for use on farms or ranches – as such 

this is “no anticipated effects on soil organisms, crops, or livestock.” (Petition Page 6). However, 

since this product could be used on fruits and vegetables, there is the possibility that its use 

either as a first step in field sanitization or during on-farm harvesting could result in 

environmental release other than through wastewater treatment systems.

2. What is the toxicity and mode of action of the substance and of its breakdown products or any 

contaminants, and their persistence and areas of concentration in the environment? 

[§6518(m)(2)]

 The technical report (TR) describes the mode of action as follows:

The silver ion is well known to be effective against a broad range of microorganisms. The 

antimicrobial action of silver ions is multifaceted due to strong interactions with the purine and 

pyrimidine DNA bases and thiol groups (i.e., -SH or sulfhydryl groups) present in enzymes and 

proteins within the microorganism (Izatt et al. 1971, Bragg and Rainnie 1974). These interactions 

markedly inhibit bacterial growth (Richards et al. 1984). Silver ions inhibit cell division, damage 

the cellular envelope, and create structural abnormalities that ultimately result in microbial 

death (Jung et al. 2008). 
The citrate counter ion also significantly contributes to the efficacy of the silver ions 

antimicrobial properties. Citrate ions stabilize the ionic form and antimicrobial properties of 

silver(+1), as they do not show a tendency to be oxidized by silver ions (Ag+) which results in 

Ago (Djokić 2008). Citric acid is a major constituent of the Kreb’s cycle, providing many 

precursors required for energy metabolism. It is readily recognized by bacteria as either a sole 

source of carbon and energy or as a co-metabolite in the presence of a food source, such as 

glucose. Thus, bacteria have both passive diffusional and active transport mechanisms for 

incorporation of citrate, which increases the permeability of the antimicrobial silver ion when it 

serves as a citrate cofactor (MacDonald and Gerhardt 1958, Korithoski et al. 2005, Pudlik and 

Lolkema 2011, Mortera et al. 2013). (TR 165-181)

The TR describes concerns with silver being considered toxic hazardous waste at certain levels:

Silver is classified by the EPA as a toxic hazardous waste if detected at 5 mg/L by Toxicity 

Characteristic Leaching Procedure-EPA method 1311 (EPA HW No. D011; 40 CFR 261.24). 

According to the 1992 Reregistration Eligibility Decision for silver (EPA-738-F-93-005), the EPA 

determined that the available acute toxicity data indicate that silver, which persists in the 

aquatic environment, is highly toxic to fish, aquatic invertebrates, and estuarine organisms. The 

active disinfectant ingredient, silver dihydrogen citrate (SDC), has an acute LC50 for freshwater 

fish that ranges from 3.9 to 280 μg/L (ppb). 

According to classification provided to the European Chemicals Agency (ECHA), silver 

dihydrogen citrate (i.e., citric acid and silver citrate EC List No. 460-890-5) is classified as Aquatic 

Chronic 1 and very toxic to aquatic life with long lasting effects (ECHA 2017). (TR 328-337)

The TR describes the other components of SDC as low concern:

The environmental assessments also concluded that the remaining components, citric acid (21 

CFR 339 184.1033) and sodium lauryl sulfate (21 CFR 172.822), are of a low order of 

environmental toxicity and the 340 potential impacts from use of the product in the intended 

applications are well within safe thresholds. (TR 339-341)

3. Describe the probability of environmental contamination during manufacture, use, misuse or 

disposal of such substance? [§6518(m)(3)]

The TR describes the environmental contamination during use and disposal as follows: The 

environmental impacts of the product from its intended uses have been evaluated by both FDA 

and EPA. FDA reviewed the environmental impacts resulting from use in poultry and produce 

processing, while EPA reviewed the impacts as part of the pesticide registration process. During 

the treatment of the process water at on-site wastewater treatment facilities, the silver 

component is expected to partition to sludge (94 %) and waste water (6 %) with environmental 

introduction concentrations of 238 nanograms (ng) per liter (L) and 1.5 ng/L, respectively (US 

FDA 2015). The concentration of silver in the sludge is 20,000 times lower than the level 

requiring disposal as toxic waste (US FDA 2015). Furthermore, the concentration of silver in 

waste water is approximately 200 times less than naturally occurring levels of silver in the 

environment in surface waters (0.2-0.3 μg/L) and is not predicted to impact the natural variation 

of background silver (US FDA 2015). These environmental assessments, with the FDA’s Findings 

of No Significant Impact (FONSI) concluded that silver dihydrogen citrate, when used as 

intended, does not present any significant environmental impacts. However, the fate of the 

silver component when used in facilities without on-site water treatment is unclear (public 

comment, Fall 2018 NOSB meeting).
The toxicity of silver in the aquatic environment is a concern with this substance but as 

described in the TR based on FDA evaluations, the waste water is released at a level below 

naturally occurring background levels of silver and is not expected to impact levels of silver 

found in the environment. Once again, it is unknown what the fate of silver is in facilities that 

do not have a wastewater treatment system, but instead rely on septic or other disposal 

systems. The petitioner notes that SDC might be used in early processing stages and these 

stages could potentially occur on farm during harvesting or prior to transport to a packing 

facility. 

The environmental impacts of manufacturing or misuse were not described. 

4. Discuss the effect of the substance on human health. [§6517 (c)(1)(A)(i); §6517 (c)(2)(A)(i); 

§6518(m)(4)].

The TR describes the impacts on human heath as follows:

Antimicrobial agents are used in the production and processing of agricultural products due to 

their effectiveness to kill or inhibit growth of microorganisms in and on foods. This is done to 

improve food safety for the consumer, as well as to extend the shelf life of food products. There 

are no known reported positive or adverse effects on human health from use of silver 

dihydrogen citrate. The high-grade silver and citric acid (used electrolytically to prepare silver 

dihydrogen citrate) have some potential adverse effects on human health. Citric acid is an 

irritant of the skin, eyes, and respiratory tract; and chronic exposure to silver and silver salts is 

most commonly associated with a permanent grey or blue discoloration of the skin (i.e., argyria) 

and other organs (ATSDR 1990, White et al. 2003, Drake and Hazelwood 2005), but the EPA 

considers the effect to be a cosmetic and not a toxicological effect and has approved pesticide 

registrations on the basis that using the product within safe regulatory levels prevents this 

effect. 

In general, silver has low acute human toxicity. It has been placed in the EPA Toxicity Category III 

for acute oral and dermal toxicity, but it is not an eye or skin irritant (Toxicity Category IV). Silver 

is also not a skin sensitizer. Although repeated contact may cause argyria, this is highly unlikely 

to be a concern at the highly diluted levels used in food facilities. The EPA has summarized its 

review of the toxicity data for silver and silver compounds as part of a recent re-registration 

process evaluating the effects on human health from pesticidal use (US EPA 1993). The EPA 

concluded that no new toxicity studies were required for non-zeolite silver compounds other 

than a repeat dose inhalation study for silver aerosols. There are also some reports that suggest 

exposure to high levels of silver salts and other soluble forms of silver may produce other toxic 

effects, including liver and kidney damage, irritation of the eyes, skin, respiratory, and intestinal 

tract, and changes in blood cells (Drake and Hazelwood 2005).

The safety of the petitioned substance for use in processing of poultry and produce for human 

consumption has been evaluated by FDA through FCNs 1768, 1569, and 1600. The product’s use 

in food contact surface sanitization has been evaluated by EPA through the pesticide 

registration process and through evaluation for the exemption from the requirement of a 

tolerance of silver in the form of silver dihydrogen citrate. Exposure to silver from the intended 

use of SDC presents no concern for the safety of human health or the environment, as 

established by FDA through its review of FCNs 1768, 1569, and 1600. The effective FCNs 

represent FDA’s conclusion that the intended uses of SDC are safe for human health, while 
FDA’s environmental reviews concluded that allowing these FCNs to become effective does not 

significantly affect the quality of the human environment. A safety assessment for citric acid is 

not included because FDA has affirmed the substance as generally recognized as safe for direct 

use in human food under 21 CFR 184.1033. (TR 351-384)

Silver is stated to be low acute human toxicity but has been placed on an EPA list for acute oral 

and dermal toxicity. It is not an eye or skin irritant. Exposure to chronic high levels of SDC can 

result in liver and kidney damage, irritation of bodily organs and changes in blood cells. It is 

unclear from the technical report if usage in described food sanitation applications is likely to 

result in chronic high-level exposure for workers. 

5. Discuss any effects the substance may have on biological and chemical interactions in the 

agroecosystem, including the physiological effects of the substance on soil organisms (including 

the salt index and solubility of the soil), crops and livestock. [§6518(m)(5)] 

See Questions 2 and 3. Additionally, this product is intended for processing use and not for use 

on farms or ranches – as such there is “no anticipated effects on soil organisms, crops, or 

livestock.” As noted in Question 3, this product could be used early in the harvesting/processing 

process and use of this product in facilities not connected with waste water treatment systems 

could cause environmental contamination and degradation.

6. Are there any adverse impacts on biodiversity? (§205.200)

See Questions 2 and 3. 

Category 3: Alternatives/Compatibility

1. Are there alternatives to using the substance? Evaluate alternative practices as well as nonsynthetic and synthetic available materials. [§6518(m)(6)]

 The TR describes sanitation practices and use of SDC as follows: 

When processing agricultural products, biocides like SDC are paramount in ensuring the safety 

of consumers. There is no reported literature describing other antimicrobial practices that are 

available for direct and indirect food contact sanitization in the processing of agricultural 

products other than the application of biocide solutions. (TR 385-388)

 The TR describes alternative materials as follows: 

There are other antimicrobial products available for use in organic agricultural processing and 

sanitization of food contact surfaces: acidified sodium chlorite (NaClO2), chlorine, ozone, and 

peroxy derivatives (7 CFR 205.605). (TR 388-390)

Despite available information and government programs’ efforts to reduce the incidence of 

Salmonella, it continues to be a concern for the meat and poultry industries. Organic acids are 

excellent antimicrobials against bacteria including Salmonella (Mani-López et al. 2012). Organic 

acids offer several advantages as antimicrobials because they are GRAS, have no limited 

acceptable daily intake, are low-cost, easy to manipulate, and effect minor sensory changes on 

the product. For example, an application of 2% acetic acid reduced the incidence of Salmonella

on pork cheek meat in addition to significantly reducing aerobic plate and coliform counts 
(Frederick et al. 1994) More than one treatment was found to sometimes help on the bacterial 

reduction and produces lesser effects on food quality. Also, poultry scald water containing 0.1% 

acetic acid at 52 C decreased levels of S. Typhimurium and Campylobacter jejuni (Okrend et al. 

1986). However, it is important to use these acids according to good manufacture practices to 

avoid the development of Salmonella strains resistant to acidic conditions.

Lactic acid, produced from fermentation, is currently listed on the National List (7 CFR 205.605(a)) 

as a non-synthetic material with no restrictions on use and is established as GRAS for using lactic 

acid as an antimicrobial agent as defined in 21 CFR 170.3(o)(2). The use of lactic acid as an 

antimicrobial agent is limited to meat products. Lactic acid has been found to be more effective 

than chlorine treatments of raw meat in poultry processing facilities (Killinger et al. 2010). The 

acidic nature imparts a mellow and lasting sourness to many products including confectionery.

However, on the National List, there are some synthetic substances allowed as disinfectants and 

sanitizers for use on food contact surfaces. These are listed under the 7 CFR 205.605 which 

delineates the nonagricultural (nonorganic) substances that may be used as ingredients in or on 

processed products that are listed as “organic” or as “made with organic [ingredients or food 

groups].” 

For example, peracetic acid can be substituted for SDC (7 CFR 205.605(b)). Peracetic acid is a 

mixture of acetic acid and hydrogen peroxide. It is a very strong oxidizing agent and has a strong 

pungent acetic acid odor. The primary mode of action is oxidation, which differs from SDC. In 

addition, peracetic acid is considered environmentally safe. Acidified sodium chlorite (using citric 

acid) and chlorine dioxide, which have the same mode of action as peracetic acid, can also substitute 

for SDC. (See the NOP petitioned substances database.) 

However, bacterial resistance to traditional agricultural biocides is of growing concern (SCENIHR 

2010). A number of gram-positive, vegetative bacteria have been isolated from equipment that used 

chlorine dioxide for high-level disinfection, and several strains, Bacillus subtilis and Micrococcus 

luteus, showed stable high-level resistance to the standard use concentration of chlorine dioxide

(Martin et al. 2008). The Bacillus isolate was also cross-resistant to hydrogen peroxide (7.5%) 

(Martin et al. 2008). Such reports of bacterial resistance have not been reported for the petitioned 

substance, although several public commenters during the Fall 2018 NOSB meeting cited research 

showing potential bacterial resistance to silver ions

The United States Food and Drug Administration (FDA) regulations allow a number of uses for 

ethanol in food preparation/storage for humans and animals. For humans, FDA considers ethanol to 

be “Generally Recognized As Safe” (GRAS) when added directly to human food (21 CFR 184.1293). 

Ethanol is an approved synthetic substance on the National List for organic livestock production as a 

disinfectant and sanitizer only (7 CFR 205.603). In addition, ethanol is an approved synthetic 

substance on the National List for organic crop production when used as an algicide, disinfectant, 

and sanitizer, including the cleaning of irrigation systems (7 CFR 205.601). Alcohols, including 

ethanol and isopropanol, are capable of providing rapid broad-spectrum antimicrobial activity 

against vegetative bacteria, viruses and fungi, but lack activity against bacterial spores (McDonnell 

and Russell 1999). The antimicrobial action of ethanol is due to rapid denaturation of proteins. A 

study found that a 7% ethanol solution prevented the growth of four common foodborne 

microorganisms: Listeria monocytogenes, Salmonella typhimurium, Staphylococcus aureus and 

Escherichia coli O157:H7 (Ahn et al. 1999), however, the CDC recommends against the use of 

ethanol or isopropanol as the principal sterilizing agent because these alcohols are insufficiently 
sporicidal (i.e., spore killing) and cannot penetrate protein-rich materials (CDC 2008). Other 

shortcomings of ethanol are that it can damage rubber and plastic tubing after prolonged use, is 

highly flammable and must be stored in cool, well-ventilated areas, and evaporates quickly due to its 

high volatility, which makes extended exposure time difficult to achieve (CDC 2008)

There are no literature reports to our knowledge that directly compare the efficacy of SDC to that of 

other organically allowed synthetic substances (e.g., chlorine dioxide, acidified sodium chlorite, 

ozone, etc.). One important distinction of SDC from these common synthetic substances for 

disinfection of food and food contact surfaces is the action of the substance. Most of the common 

synthetic substances are strong oxidizers; thus their antimicrobial efficacy generally increases with 

oxidation potential (i.e., chlorine dioxide < acidified sodium chlorite < ozone). The efficacy of SDC 

derives from a different mechanism of action, interference with cellular processes. In a closely 

related study, the antimicrobial effects of chlorine (Cl2), an oxidizer, and Ag+ ions on bacterial 

biofilms were compared (Kim et al. 2008). The antimicrobial activities on biofilm cells were 

investigated by three methods, each of which used a different analytical principle for the 

determination of antimicrobial activity. The study found that the resistance of the biofilm cells to 

the oxidant, chlorine, was increased almost 250 times compared with the resistance to the Ag+ ion. 

Thus, due to the different mode of action, Ag+ ions and SDC, in particular, represent a viable 

alternative for eliminating pathogenic bacteria that demonstrate resistance to common oxidizing 

antibacterial agents.

In summary, there is no literature that directly compares SDC to other organically allowed synthetic 

substances. Acetic and Lactic acid are effective in meat environments but lactic acid is solely limited 

to this manufacturing environment. There are concerns of acid resistant salmonella in certain 

manufacturing conditions. Chlorine, peracetic acid and acidified sodium chlorite are effective 

oxidative alternatives, however there is a growing concern over resistance of bacteria to oxidative 

reactions. While ethanol and isopropanol are effective against some pathogens they are not

effective against bacterial spores – and are not recommended by the CDC as principle sanitizing 

agents. SDC works using an alternative mode of action to oxidation antibacterial agents – silver 

compounds so far have not experienced the growing resistance to treatment as seen with oxidation 

antibacterial agents. 

2. For Livestock substances, and Nonsynthetic substances used in Handling: In balancing the 

responses to the criteria above, is the substance compatible with a system of sustainable 

agriculture? [§6518(m)(7)]

N/A

Category 4: Additional criteria for synthetic substances used in Handling (does not apply to 

nonsynthetic or agricultural substances used in organic handling):

Describe how the petitioned substance meets or fails to meet each numbered criterion.

1. The substance cannot be produced from a natural source and there are no organic substitutes; 

(§205.600(b)(1))

 The substance cannot be produced from natural sources. See Category 1 question 2. 

 Alternatives substances are discussed in Category 3 Question 1. 
The technical report discusses other alternative practices as follows: 

While agricultural and/or natural antimicrobials may be effective in one way, they may be

ineffective in another and do not possess broad spectrum antimicrobial properties (Sebranek 

and Bacus 2007). This stresses the necessity of further research in order to ensure that the food

safety of these materials is properly assessed. While current research suggeststhat natural plant

extracts can be effective in controlling pathogens in meat products, the most favorable results

tend to result from multiple-barrier food preservation systems, which use combinations of

agricultural and/or natural antimicrobials and sodium or potassium lactate (or other synthetic

antimicrobial ingredients). However, decreasing the shelf life of a product to accommodate the

strict use of natural antimicrobials is another option. A survey of organic agricultural 

antimicrobials is discussed below. 

The USDA organic regulations do not permit the addition of nitrite to organic processed meat.

Alternative methods like the use of celery powder, which is listed at 7 CFR Part 205.606 and

allowed for use in productslabeled as “Organic” only when an organic form is not

commercially available, are commonly used in meat products. Trials studying natural 

antimicrobials for the inhibition of Listeria monocytogenes on naturally cured frankfurters have 

been conducted (Xi et al. 2013). Using celery powder containing 12,000 ppm of nitrite, the

concentration of nitrite (when the celery powder was used at 0.4% of the frankfurter

formulation) resulted in 48 ppm of nitrite added to the frankfurter mixture. In a conventional

curing process, 156 ppm of nitrite is added. The research found that the celery powder

achieved the expected color, flavor and other properties of cured meats, but it resulted in

lower nitrite levels than occurred with the use of syntheticpreservatives.

In the same study by Iowa State University in 2013, powdered concentratesfrom cranberries,

cherries, limes and a blend of cherry, lime and vinegar were evaluated alone and in various

combinationsfor antimicrobial impact on the growth of L. monocytogenes in naturally cured

frankfurters (Xi et al. 2013). The results showed that cranberry powder at 3% of the

formulation, combined with celery powder, achieved inhibition of L. monocytogenes following

the inoculation of naturally cured frankfurtersthat was equivalent to that of conventionally

cured frankfurters during 49 days of refrigerated storage. Cranberry powder at 1% and 2% in

combination with other natural antimicrobials inhibited growth for up to 35 days, while the

naturally cured frankfurters without additional antimicrobial ingredients showed growth after

28 days. However, quality assessment of the productsshowed that 3% cranberry powder was

detrimental to the color and sensory and textural attributes of the frankfurters, possibly due to

the acidic nature of the cranberry concentrate. It was concluded that, while cranberry

concentrate has potential as a natural antimicrobial, it is necessary to develop a means of

compensating for the acidic nature of this ingredient to achieve practical applications in

organic cured meat products. In addition, for the meat to maintain its organic status, the

cranberry powder would also need to be a certified organic ingredient, and, per the

requirements of 7 CFR 205.606, attempts would need to be made to source organic celery

powder.

The effectiveness of essential oils in controlling L. monocytogenes has also been investigated 

(Campos et al. 2011). The results of the study were promising; however, in many instances,

combinations of additives or preservative treatments worked best because the efficacy of the

antimicrobials can be influenced by the chemical composition and the physical conditions of

variousfoods. Essential oils (EOs) are oily liquid mixes of volatile and complex compounds that

are extracted from different parts of aromatic plants. They are synthesized by plants as
secondary metabolites and can be obtained mainly by steam distillation or super critical fluid

extraction. Essential oils can contain 20-60 components, depending on the material they come

from and the extraction method used. Terpenes and terpenoids make up the constitute 

majority of the components with the remainder consisting of aromatic and aliphatic 

compounds of low molecular weight.

Essential oil efficacy against Listeria growth in laboratory media was highly variable (Campos et 

al. 2011). EOs of bay, coriander, cinnamon, clove, licorice, nutmeg, pepper, oregano, winter 

savory, spruce and thyme showed the highest inhibitory activity. The effectiveness of oils of 

basil, lemon balm, marjoram, mastic tree, rosemary and sage were lower than those mentioned 

above, whereas Listeria showed high resistance to EOs of aniseed, caraway, fennel, garlic, 

ginger, onion and parsley.

According to the research, the antimicrobial activity of EOs is largely dependent on their 

composition; however, the mechanism of antimicrobial action of EOs is not well understood. 

Inhibitory actions are mostly related to the identity of the majority terpenes and terpenoid 

components, but the minor components have a strong influence on the effectiveness of their 

antimicrobial action. The main components often consist of: carvacrol, thymol, linalool, 

eugenol, trans-cinnamaldehyde, p-cymene, 1,8-cineole (eucalyptol) and γ-terpinene, and the 

research suggests that several components of EOs are involved in the fixation on cell walls and 

cellular distribution. It’s reported that EO components may degrade the cell wall, damage the 

cytoplasmic membrane and proteins of the membrane, leak vital intracellular compounds, 

coagulate cytoplasm and deplete the proton motive force, and that EOs also interact with one 

another, potentially leading to synergistic antimicrobial effects between various oils (Campos et 

al. 2011). For example, the growth of L. monocytogenes was suppressed in laboratory media 

more when a combination of oils was used (oils of oregano and rosemary; oils of basil, 

rosemary or sage; and oils of rosemary and licorice) than when these oils were used alone.

Further results in various samples suggested that EOs have lower activity in foods with high fat 

content. This may be due to: (i) EO dissolution in the lipid fraction of the food, decreasing the 

concentration in the aqueous phase, together with antimicrobial action; (ii) the reduced water 

content in foods, particularly in fatty foods, in relation to culture media, which may slow down 

the movement of the preservative to the active site in the microbial cell; and (iii) the presence 

of fat in the food which may produce a protective layer around the bacteria (Campos et al. 

2011).

Storage temperature, pH, physical structure of food, fat, protein, sugar content, and sensory 

properties all need to be considered when deciding whether EOs will be affective for controlling 

pathogens. It was reported that chicken frankfurters treated with 2% v/w of clove oil were 

unacceptable to the consumer, whereas samples with 1% were accepted. The latter level had 

effective antilisterial activity in the food. It was found that combining EOs would allow the use 

of lower levels to reduce Listeria growth, minimizing the unacceptable sensory changes in the 

food. Indirect uses of EOs, for example in water to wash vegetables similar to the use of 

chlorine, or in the impregnation of porous surface of wood in cheese ripening to improve 

sanitary safety, are also being considered. (TR 470-552)

2. The substance's manufacture, use, and disposal do not have adverse effects on the environment 

and are done in a manner compatible with organic handling; (§205.600(b)(2))

Refer to Question 3 of Category 2. 
3. The substance's primary use is not as a preservative or to recreate or improve flavors, colors, 

textures, or nutritive value lost during processing, except where the replacement of nutrients is 

required by law; (§205.600(b)(4))

According to the technical report: “There is no information to suggest that silver dihydrogen 

citrate is used to recreate or improve flavors, colors, textures, or nutritive values lost in the 

processing of agricultural products. The petition requests to permit the use of SDC solutions as a 

processing aid in the wash and/or rinse water for direct and indirect food contact. (TR 290-293)”

4. The substance is listed as generally recognized as safe (GRAS) by the Food and Drug Administration 

(FDA) when used in accordance with FDA's good manufacturing practices (GMP) and contains no 

residues of heavy metals or other contaminants in excess of tolerances set by FDA; 

(§205.600(b)(5))

According to the technical report, silver dihydrogen citrate is not categorized as generally 

recognized as safe (GRAS). The USDA Food Safety Inspection Service has reviewed and approved 

silver dihydrogen citrate for use as a food contact substance in applications for treating poultry 

(FCN 1569 and FCN 1768) and fruits and vegetables (FCN 1600). The substance has been reviewed 

and approved by the EPA for use as an antimicrobial, disinfectant, fungicide, and virucide, and 

food contact surface sanitizer (EPA Registration Nos. 72977-1, 72977-3, 72977-4, 72977-5, and 

72977-6). The substance is the subject of an exemption from tolerance for residues of silver in 

foods from food contact surface and processing equipment sanitizing applications (40 CFR 

180.950).

Silver dihydrogen citrate has been certified by NSF International, an independent public health and 

safety organization, for use as a sanitizer on all surfaces and as not always requiring a rinse in and 

around food processing areas (NSF Registration No. 144518).

The petitioned substance has been added to the list of Safe and Suitable Ingredients Used in the 

Production of Meat, Poultry, and Egg Products by the USDA (FSIS Directive 7120.1 Rev. 42).

Citric acid is affirmed by the FDA (21 CFR 184.1033) as generally recognized as safe (GRAS) and 

may be used with no limitations other than good manufacturing practice. Sodium lauryl sulfate can 

be introduced intentionally during manufacturing to act as a solution stabilizer and is permitted for 

direct addition to food for human consumption by the FDA (21 CFR 172.822). (TR 254-272)

5. The substance is essential for the handling of organically produced agricultural products. 

(§205.600(b)(6))

The decision here is to balance the environmental and human health impacts from this substance 

against the food safety benefits, considering the alternatives. Overall the environmental and 

human health risks seem low, although there are questions about the disposal of the material in 

facilities that do not include wastewater treatment systems and the potential for silver ion 

resistant bacteria. With a growing level of resistance to current antibacterial agents on this list, 

SDC appears to offer unique and necessary food safety attributes, but there are questions as to 

exposure of workers to the material as well as reducing the efficacy of silver in the treatment of 

human health concerns. Comments received from packers of organic and non-organic leafy-green 

products stated the need for this substance to reliably meet sanitation levels. Additionally, they 
commented the increased safety and preference by sanitation workforce for this material over 

alternatives on the national list. 

Concerns have been raised about nanoparticles and this substance. The petitioner states “the 

product does not contain nano silver (Petition page 7). Additionally, the technical review notes 

that nanoparticles could augment the efficacy of the SDC by increasing the concentration of silver 

– but that nanoparticles are not necessary for SDC as petitioned to be effective and alternative 

ways exist to increase silver concentration. (TR 109-121). 

6. In balancing the responses to the criteria in Categories 2, 3 and 4, is the substance compatible with 

a system of sustainable agriculture [§6518(m)(7)] and compatible with organic handling? (see NOSB 

Recommendation, Compatibility with Organic Production and Handling, April 2004) 

Human health concerns appear to be minimal according to the petitioner and the TR. However, 

several public commenters provided research to the contrary. The environmental risk of SDC 

disposal or release is unclear. 

Category 5: Additional criteria for agricultural substances used in handling (review of commercial 

unavailability of organic sources):

This section is not applicable 

1. Is the comparative description as to why the non-organic form of the material /substance is 

necessary for use in organic handling provided? 

This section is not applicable 

Does the current and historical industry information, research, or evidence provided explain how 

or why the material /substance cannot be obtained organically in the appropriate form to fulfill an 

essential function in a system of organic handling?

This section is not applicable 

2. Does the current and historical industry information, research, or evidence provided explain how 

or why the material /substance cannot be obtained organically in the appropriate quality to fulfill 

an essential function in a system of organic handling?

This section is not applicable 

3. Does the current and historical industry information, research, or evidence provided explain how 

or why the material /substance cannot be obtained organically in the appropriate quantity to fulfill 

an essential function in a system of organic handling?

This section is not applicable 

4. Does the industry information about unavailability include (but is not limited to) the following?

Regions of production (including factors such as climate and number of regions);

This section is not applicable 
a. Number of suppliers and amount produced;

b. Current and historical supplies related to weather events such as hurricanes, floods, and 

droughts that may temporarily halt production or destroy crops or supplies;

c. Trade-related issues such as evidence of hoarding, war, trade barriers, or civil unrest that 

may temporarily restrict supplies; or

d. Other issues which may present a challenge to a consistent supply?

5. In balancing the responses to the criteria in Categories 2, 3 and 5, is the substance compatible with 

a system of sustainable agriculture [§6518(m)(7)] and compatible with organic handling? (see 

NOSB Recommendation, Compatibility with Organic Production and Handling, April 2004) 

The NOSB finds merit for this material, particularly around the need for alternative sanitizers in organic 

processing and its relative minimal potential human health impacts. However, concerns linger around 

its potential impact on the environment, its compatibility with organic production given the concerns 

around nano-particles and concerns around the use of sodium lauryl sulfate in formulation. At this time 

the Subcommittee is not recommending this material for inclusion on the National List. If the noted 

concerns above can be mitigated or addressed, then the above material could be re-petitioned for 

reconsideration. 

Classification Motion: 

Motion to classify silver dihydrogen citrate as synthetic

Motion by: Tom Chapman

Seconded by: Lisa de Lima

Yes: 6 No: 0 Abstain: 0 Absent: 2 Recuse: 0 

National List Motion: 

Motion to add silver dihydrogen citrate at §205.605(b)

Motion by: Tom Chapman

Seconded by: Lisa de Lima

Yes: 0 No: 6 Abstain: 0 Absent: 2 Recuse: 0