This is a Sunset Preliminary Review by a Subcommittee of the National Organic Standards Board (NOSB). Sunset preliminary reviews are posted for 

public comment and the NOSB will refer to them to complete the sunset review process. They are not final Board recommendations or NOP policy. 

For more information, see the Sunset Review and Renewal Process fact sheet, and Federal Register notice of Sept. 16, 2013.

Sunset 2015 Review

Meeting 2 - October, 2014

Crops Subcommittee

Sulfurous Acid

August 20, 2014

As part of the National List Sunset Review process, the NOSB Crops Subcommittee has evaluated the need for the 

continued allowance for or prohibition of the following substances for use in organic crop production.

Sulfurous Acid Synthetic

Use - As plant or soil amendment. 

Listing: Sulfurous acid (CAS # 7782-99-2) - for on-farm generation of substance utilizing 99% purity elemental sulfur per 

paragraph (j)(2) of this section. 

Technical Reports: 2010 TAP; 2014 TR

Original Petition: Sulfurous Acid (2008)

Past NOSB Actions: Recommended for addition to the National List on 5/2009

Regulatory Background: Proposed rule (including justification) published 1/12/2010 (75 FR 1555). Added to National List 

7/6/2010 (75 FR 38693). 

Sunset Date: 7/7/2015

Reference 7 CFR 205.601(j)(9)

Subcommittee Review

The Crops Subcommittee believes that the full Board should have the opportunity to complete the review of each 

sunset material by voting. The NOP has stated that to do this a motion to remove should be brought from the 

Subcommittee for each substance. If the Subcommittee motion to remove fails to receive a majority, the motion will 

still be put forward to the full board for review. The motion to remove is voted by the full Board and needs to receive 

a 2/3 majority to recommend removal.

Summary:

Sulfurous acid was added to the National List in 2009, with the annotation, “on-farm generation of substance utilizing 

99% purity elemental sulfur per paragraph (j)(2) of this section.” The Crops Subcommittee has received a Technical 

Review that contains new information that needs to be considered in the Sunset review:

1. The TR contains information about environmental impacts of sulfurous acid, particularly on soil organisms;

2. There is information on alternative materials and practices that was not considered by the board in 2009;

3. It appears that sulfurous acid might be used to correct the impacts of unsustainable irrigation practices;

4. This use of sulfurous acid is not permitted in organic agriculture in other countries

The Crops Subcommittee posed the following questions in the Spring 2014 meeting announcement:

1. The Crops Subcommittee is interested in the conditions under which sulfurous acid undergoes the transformation to 

sulfate, and conditions under which that sulfate is available as a plant nutrient. The 2014 TR describes the chemistry 

of sulfurous acid in the soil at lines 64-67, 140-149, and 261-264. The subcommittee seeks comments that address 

the following questions: Are there specific soil and ecological (e.g., moisture) conditions under which the 

transformation to sulfate would be made and the sulfate made available? On the other hand, are there soil and 

ecological conditions that would result in the build-up of hydrogen sulfite, sulfate, or other products of sulfurous 
acid? Are there management practices that can be used by the grower to affect whether the transformation occurs 

and the sulfate is available to crops? Are there evaluation tools that can be used by farmers and certifiers to 

determine which of the above soil conditions are present? 

2. The subcommittee would like public input on whether sulfurous acid is used to remedy conditions resulting from 

unsustainable agricultural practices. If so, how can this be evaluated by the NOSB in the sunset review of this 

material? 

The Crops Subcommittee received 8 comments in favor of relisting sulfurous acid and 5 comments opposing relisting. 

Comments in favor of relisting included the following:

1. Sulfurous acid is tool organic growers can use to counteract soil salinity and alkalinity.

2. Sulfurous acid does not act as a sulfate fertilizer because the sulfate is present only at a parts per million level while 

sulfur is a secondary level nutrient (along with calcium and magnesium) that is needed at much higher quantities to 

influence plant growth.

3. Sulfurous acid is a water treatment for poor quality irrigation waters; it is not a remedy for unsustainable farming 

practices.

4. The soil and ecological conditions resulting in the build-up of hydrogen sulfite, sulfate, or other products of sulfurous 

acid would only happen in anaerobic soils with complete water saturation. This is unlikely to happen in the western 

portion of the United States because farmers here are very familiar with the conditions under which irrigation is 

needed.

5. It increases the sustainability of agricultural soils in alkaline environments as its use keeps soil pore space open to 

the air and water helping to leach away toxic salts.

6. Many small berry growers –especially blueberry growers—depend on this technology.

Comments opposing relisting included the following:

1. Specific uses must be delineated as well as conditions under which it can be used.

2. International standards do not allow sulfurous acid in crop production.

3. There are potential adverse impacts that have not been evaluated by the NOSB.

4. The NOSB needs to ask whether the “need” for sulfurous acid reflects unsustainable farming practices.

Conclusion

In reviewing the 2014 Technical Review and materials submitted by commenters, the Crops Subcommittee finds new 

evidence relating to OFPA criteria. There are concerns about compatibility with organic and sustainable systems, and 

also evidence of overall value to organic agriculture especially when saline/alkaline irrigation water quality problems 

exist. For more information, see the attached evaluation checklist. The subcommittee supports research to gather 

additional information needed to address the issues in the checklist.

Motion to Remove:

This proposal to remove will be considered by the NOSB at its public meeting. 

Based on the Subcommittee’s review, the Subcommittee proposes removal of this substance from the National List 

based on the following criteria in the Organic Foods Production Act (OFPA): [OFPA criteria at 7 U.S.C. 6158(m), (7) its 

compatibility with a system of sustainable agriculture.

Motion to remove Sulfurous Acid from the National List

Motion by: John Foster

Seconded by: Harold Austin

Yes: 4 No: 3 Abstain: 0 Recuse: 0 Absent: 0
Minority Statement on Motion to Remove

While the minority of the CS agrees with the majority that the full NOSB should vote on sunset materials, in voting 

against this motion it is following what we believe are required procedure of AMS/USDA as established by the 

September 16, 2013 Federal Register notice (78 FR 56811), which states that motions to remove be justified by criteria 

established by the Organic Foods Production Act. Because of concern that a change in NOSB procedures should be 

disclosed to the public before taking effect, the minority does not accept the compatibility criteria from 7 U.S.C. 6158(m)

(7) that was provided in this case. Furthermore, AMS/NOP has said that no action by the NOSB maintains a sunset 

material on the National List.
Evaluation Criteria (checklist for criteria in each category)

Criteria Satisfied? 

1. Impact on Humans and Environment ☒ Yes ☐ No ☐ N/A 

2. Essential & Availability Criteria ☐ Yes ☒ No ☐ N/A

3. Compatibility & Consistency ☐ Yes ☒ No ☐ N/A 

Substance Fails Criteria Category: 2, 3

NOSB Evaluation Criteria for Substances Added To the National List (Optional Checklist)

Category 1. Adverse impacts on humans or the environment? Sulfurous Acid

Question Yes No N/A Comments/Documentation (TAP; petition; 

regulatory agency; other)

1. Is there a probability of environmental 

contamination during use or misuse? 

[§6518(m)(3)]

X There is a potential for damage to the local 

ecosystems from improperly maintained 

sulfurous acid generators. TR lines 330-331.

2. Is there a probability of environmental 

contamination during, manufacture or 

disposal? [§6518(m)(3)]

X Depends on fossil fuel production. TR lines 

251-253.

3. Are there any adverse impacts on 

biodiversity? (§205.200)

Overuse of sulfurous acid and subsequent 

acidification will cause the metabolism of 

microorganisms involved in compost and 

organic matter breakdown in treated 

streams and runoffs to be suppressed along 

the acidity gradient, and can lead to a 

decrease in humus production (Simon, et al., 

2009). TR lines 333-336.

4. Does the substance contain inerts classified 

by EPA as ‘inerts of toxicological concern’? 

[§6517 (c)(1)(B)(ii)]

X TR line 229.

5. Is there potential for detrimental chemical 

interaction with other materials used in 

organic farming systems?

[§6518(m)(1)]

? The primary purpose of sulfurous acid for 

crop production is reducing the pH of 

irrigation water to alleviate the effects of 

specific saline/sodic soil conditions or the 

effects caused by saline or sodic irrigation. TR 

lines 295-297

6. Is there a toxic or other adverse action of the 

material or its breakdown products?

[§6518(m)(2)]

X Sulfurous acid is slightly irritating to the skin, 

and strongly irritating to the eyes. TR lines 

364-365.

7. Is there persistence or concentration of the 

material or breakdown products in the 

environment? [§6518(m)(2)]

X Hydrogen sulfite present in the solution is 

metabolized by sulfite reducing bacteria and 

plants that recycle sulfurous acid into 

bioavailable sulfur compounds. Water and 

other dissolved compounds leach into the 

soils. Functionally, sulfurous acid serves to 

condition soils by adjusting pH. TR lines 261-

264.
8. Would the use of the substance be harmful 

to human health or the environment? 

[§6517 (c)(1)(A)(i); §6517 (c)(2)(A)(i); 

§6518(m)(4)]

? It would be harmful if it discourages adoption 

of farm methods that prevent alkalinization 

and salinization of the soil, which have 

broader impacts than the particular farm 

where sulfurous acid might be used – such as 

creating a progressively more alkaline 

groundwater supply.

9. Are there adverse biological and chemical 

interactions in the agro-ecosystem? 

[§6518(m)(5)]

? Overuse of sulfurous acid and subsequent 

acidification will cause the metabolism of 

microorganisms involved in compost and 

organic matter breakdown in treated 

streams and runoffs to be suppressed along 

the acidity gradient, and can lead to a 

decrease in humus production (Simon, et al., 

2009). TR lines 333-336.

10. Are there detrimental physiological effects 

on soil organisms, crops, or livestock? 

[§6518(m)(5)]

? Overuse of sulfurous acid and subsequent 

acidification will cause the metabolism of 

microorganisms involved in compost and 

organic matter breakdown in treated 

streams and runoffs to be suppressed along 

the acidity gradient, and can lead to a 

decrease in humus production (Simon, et al., 

2009). TR lines 333-336.

Category 2. Is the Substance Essential for Organic Production? Sulfurous Acid

Question Yes No N/A Comments/Documentation (TAP; petition; 

regulatory agency; other)

1. Is the substance agricultural? [§6502(1)] X

2. Is the substance formulated or 

manufactured by a chemical process? 

[§6502(21)]

X TR lines 250-256.

3. Is the substance formulated or 

manufactured by a process that chemically 

changes a substance extracted from 

naturally occurring plant, animal, or mineral 

sources? 

[§6502(21)]

X Generally, the source of the sulfur is from 

fossil fuels. TR lines 250-253.

4. Is the substance created by naturally 

occurring biological processes? 

[§6502(21)]

X See questions #2 and 3.

5. Is there a natural source of the substance? 

[§ 205.600(b)(1)]

X

6. Is there an organic substitute? 

[§205.600(b)(1)]

X

7. Is there a wholly natural substitute product?

[§6517(c)(1)(A)(ii)]

X Organic matter, pure sulfur, gypsum, 

compost, citric acid. TR lines 385-388.

8. Are there any alternative substances? 

[§6518(m)(6)]

X See #7. Also, aquatic plant extracts, 

elemental sulfur, lignin sulfonate, humic 

acids and liquid fish extracts TR lines 395-

397.
9. Are there other practices that would make 

the substance unnecessary? [§6518(m)(6)]

X Proper irrigation, control of 

evapotranspiration, lining irrigation canals, 

salt-tolerant crops. TR lines 408-426.

Category 3. Is the substance compatible with organic production practices? Sulfurous Acid

Question Yes No N/A Comments/Documentation (TAP; petition; 

regulatory agency; other)

1. Is the substance consistent with organic

farming and handling? 

[§6517(c)(1)(A)(iii); 6517(c)(2)(A)(ii)]

X Not permitted in other countries. TR lines 

184-215. IFOAM specifically states, 

“Operators shall prevent or remedy soil or 

water salinization where these pose a 

problem. Sulfurous acid is used as a remedy 

for salinization of soil” TR lines 214-215

Synthetic fertilizer. TR lines 146-147; 261-

263.

2. Is the substance compatible with a system of 

sustainable agriculture? [§6518(m)(7)]

X Used to correct impacts of poor irrigation 

practices. TR lines 127-141.

3. If used in livestock feed or pet food, Is the 

nutritional quality of the food maintained 

with the substance? [§205.600(b)(3)]

X

4. If used in livestock feed or pet food, Is the 

primary use as a preservative? 

[§205.600(b)(4)]

X

5. If used in livestock feed or pet food, Is the 

primary use to recreate or improve flavors, 

colors, textures, or nutritive value lost in 

processing (except when required by law)? 

[§205.600(b)(4)]

X

6. 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

X

toxins derived from bacteria X

pheromones, soaps, horticultural oils, 

fish emulsions, treated seed, vitamins 

and minerals

X

livestock parasiticides and medicines X

production aids including netting, tree 

wraps and seals, insect traps, sticky 

barriers, row covers, and equipment 

cleansers

X