United States Environmental Protection Agency Office of Pesticide Programs

Questions & Answers on the Chlorine Gas Reregistration Eligibility Decision (RED)

Chlorine gas is the most widely used disinfectant of water and food processing systems. EPA has completed a review of its human health and environmental effects, and determined that chlorine is eligible for reregistration. As a condition of reregistration, EPA is requiring additional label changes and data collection. This Questions and Answers document answers the most commonly asked questions regarding chlorine and the Agency's Reregistration Eligibility Decision (RED).

  1. What is chlorine gas and what purpose does it serve?
  2. How is the use of chlorine gas regulated?
  3. Are there any exposure risks?
  4. What is EPA doing to reduce exposure risks?
  5. What does this all mean for the reregistration of chlorine products?
  6. Why did the EPA wait several years to issue the Chlorine Gas RED?
  7. How may I obtain a copy of the RED document and whom may I contact for further information?

1. What is chlorine gas and what purpose does it serve?

First registered in the United States in 1948 as a disinfectant for use in swimming pools, drinking water, cooling towers, and sewage systems, chlorine gas is a very widely used pesticide. It is now also used to disinfect ornamental ponds and aquaria, wastewater, and other types of water reservoirs. It is also used as a disinfectant, microbistat/microbicide, and algaecide in food processing systems, pulp and paper mill systems, and commercial and industrial cooling systems. Chlorine gas is used in washing meat, fresh produce, and seeds to control decay-causing microorganisms. With an annual usage of about 1 billion pounds per year, chlorine gas is the most heavily used pesticide in the United States. At least 95% of this usage is for "public health" related uses.

2. How is the use of chlorine gas regulated?

Several Federal Agencies and offices within EPA are involved with regulating the uses of chlorine gas. EPA’s Office of Water regulates chlorine in drinking water supplies, in coordination with its Office of Pesticide Programs (OPP), since chlorine serves as a biocide when added to drinking water. EPA’s Office of Pesticide Programs also regulates occupational exposures associated with the pesticidal uses of chlorine. Some aspects of chlorine handling are also covered by the Occupational Safety and Health Administration. EPA’s Office of Pollution Prevention and Toxics has regulatory authority over chlorine’s non-pesticidal, chemical reactant uses (such as the manufacture of plastics). The use of chlorine gas as a food contact surface sanitizer on food, meat, or poultry processing premises and equipment is under the Food and Drug Administration’s (FDA’s) regulatory jurisdiction. This sharing of regulatory responsibility across offices and agencies makes coordination crucial. The Office of Pesticide Programs consulted with these groups in developing and completing the final chlorine gas RED.

3. Are there any exposure risks?

Accidental ingestion: There are concerns about toxicity if chlorine products, such as household bleach, are ingested. Medical reports have indicated that such exposure results in temporary and easily treated irritation of the digestive tract and stomach, as well as irritation to the mouth and throat.

Drinking Water Exposure: EPA's Office of Drinking Water is primarily responsible for assessing the risks associated with consumption of drinking water. They have concluded that it is safe to drink water containing chlorine residues within the limit of the established standard (that is, residues at or below the Maximum Residual Disinfectant Level (MRDL) of 4 mg/L).

Residential Exposure: Except for rare instances involving special sensitivities, bathing, and showering do not result in significant exposures to chlorine, or pose significant risks. Similarly, the Agency does not expect significant exposure or risks to those swimming in chlorine-treated residential pools, as long as product label requirements are followed. There is potential for swimmer and bystander exposure to chlorine gas releases from in-place chlorinator systems at public and/or commercial swimming pools due to applicator error and equipment failure.

Occupational Exposure: EPA is concerned about applicator and post-application exposure to chlorine gas, because it is highly toxic for all routes of direct exposure. Occupational exposure guidelines have been established by the Occupational Safety and Health Administration and other domestic and foreign sources. The greatest risk of poisoning accidents from chlorine is to applicators and workers in industrial food settings and water/sewage treatment plants, public and/or commercial swimming pools with chlorine gas systems, and to applicators in general.

Chlorine gas is dissolved into water through automated water injection systems in manufacturing processes or from large stationary containers, such as tank cars, tank trucks, and cylinders. It is also applied to water using smaller, portable cylinders. Given current use patterns of chlorine gas, there exists the potential for skin and inhalation exposure to applicators and other people dermally exposed to chlorinated water in certain occupational settings, particularly workers in food processing plants using concentrated chlorine solutions. Accidental exposure to chlorine gas due to equipment failure or poor maintenance application operations is also possible, especially around in-place chlorinator systems in industrial settings, water/sewage treatment plants, and at swimming pools.

4. What is EPA doing to reduce exposure risks?

To mitigate exposure risks, EPA is requiring Restricted Use Pesticide classification for the use of chlorine gas in food processing plants, public/commercial swimming pools, pulp/paper mills, and cooling towers so that, in the future, these uses will be limited to trained, certified applicators. In addition, EPA is requiring significant revisions to product labeling through its Reregistration Eligibility Decision (RED) document, so that the labels will contain sufficient site-specific use information and directions. These labeling improvements should adequately address the risks associated with water/sewage treatment and residential pool uses.

Specifically, EPA is requiring the following label changes:

  • Restricted Use Pesticide Classification - Chlorine products registered for use in non-residential swimming pools, pulp and paper mill processes, and industrial food processing plants and cooling towers are being reclassified as Restricted Use Pesticides due to chlorine's extreme acute toxicity plus many associated human poisoning incidents. Handlers and applicators of products with these uses will be required to have specific training.
  • Standard Labeling for Chlorine Products (Statement of Practical Treatment/First Aid, etc.) - Labeling formats must be modified to be consistent with the latest standards for pesticide labels.
  • Use Directions - The end-use product label must indicate specific intended uses and must provide specific directions for each use. Labeling must include detailed application and/or transfer directions.

    For specific information on these labeling requirements, please refer to the Chlorine Gas RED or the RED Fact Sheet.

5.  What does this all mean for the reregistration of chlorine products?

EPA has determined that, in accordance with the additional risk mitigation measures specified in the RED, all currently registered pesticide products containing chlorine can be used without causing unreasonable adverse effects to humans or the environment. Therefore, EPA is declaring all chlorine products eligible for reregistration. The terms of the RED state that:

Chlorine products registered for use in non-residential swimming pools, pulp and paper mill processes, and industrial food processing plants are being reclassified as Restricted Use Pesticides, due to chlorine's extreme acute toxicity. These products must bear Restricted Use Pesticide labeling no sooner than October 1, 2000, and no later than April 1, 2001.

Chlorine products registered for drinking water, sewage and waster water treatment uses, and residential pool use will not be considered Restricted Use because few related accidents or incidents of poisoning have been reported, suggesting that existing requirements are satisfactory. Additionally, for water treatment, applicators are already trained and state-certified to perform these uses.

Finally, products containing chlorine as the sole active ingredient will be reregistered once EPA's required studies, data, and label changes have been received and accepted by the Agency.

6. Why did the EPA wait several years to issue the Chlorine Gas RED?

EPA completed the Chlorine Gas RED document in late 1995, but delayed its public release in order to consider the concerns of internal and external stakeholders, particularly regarding Agency data needs with the Office of Drinking Water. While the recently published RED does include several new data collection requirements and labeling modifications, it is essentially the same document that EPA developed earlier,strengthened by additional analysis and feedback from stakeholders.

7.  How may I obtain a copy of the RED document and whom may I contact for further information?

Public Comments:

EPA is requesting public comments on the Reregistration Eligibility Decision (RED) document for Chlorine Gas, during a 60-day time period, as announced in a Notice of Availability published in the Federal Register. To obtain a copy of the RED document or to submit written comments, please contact the Pesticide Docket, Information and Record Integrity Branch, Information Resources Services Division (7502C), Office of Pesticide Programs (OPP), US EPA, Washington, DC 20460, telephone 703-305-5805.

Printed Copies:

Printed copies of the RED and fact sheet are available from EPA's National Service Center for Environmental Publications EPA/NSCEP), PO Box 42419, Cincinnati, OH 45242-0419, telephone 1-800-490-9198, fax 513-489-8695.  Following the comment period, the Chlorine Gas RED document also will be available from the National Technical Information Service (NTIS), 5285 Port Royal Road, Springfield, VA 22161, telephone 703-605-6000 or 800-553-6847.

For More Information:

For more information about EPA's pesticide reregistration program, the Chlorine Gas RED, or reregistration of individual products containing chlorine gas, please contact the Special Review and Reregistration Division (7508C), OPP, US EPA, Washington, DC 20460, telephone 703-308-8000. Electronic copies of the Chlorine Gas RED and RED fact sheet are available here on the Website at  http://www.epa.gov/REDs .

For general information on EPA's pesticide programs, visit the EPA web site at http://www.epa.gov/pesticides, or call the Communication Services Branch at 703-305-5017. 

For information about the health effects of pesticides, or for assistance in recognizing and managing pesticide poisoning symptoms, please contact the National Pesticides Telecommunications Network (NPTN). Call toll-free 1-800-858-7378, between 9:30 am and 7:30 pm Eastern Standard Time, Monday through Friday.

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