Chloropicrin

(endorsed 2011)

Guideline

Data are inadequate to set a health-based guideline for chloropicrin in drinking water.

Related chemicals

Chloropicrin (CAS 76-06-2) belongs to the fumigant class of chemicals. Other pesticides in this class include methyl bromide and sulfuryl fluoride (Tomlin 2006).

Human risk statement

There are currently insufficient data on which to base a human risk statement.

With good water quality management practices, pesticides should not be detected in source waters used for drinking water supplies. Persistent detection of pesticides may indicate inappropriate use or accidental spillage, and investigation is required in line with established procedures in the risk management plan for the particular water source.

General description

Uses: Chloropicrin is a fumigant used in soil to control soil-borne fungi, diseases and nematodes. It is also used to fumigate stored products and to treat wood poles and timbers for internal decay by fungi and insects. Because of its pungent odour, it is also used as a warning agent in combination with other fumigants. Chloropicrin, or trichloronitromethane ($\text{Cl}_3\text{CNO}_2$), is a liquid that volatilises readily when released into the atmosphere.

There are registered products containing chlorpicrin in Australia. The products are all for professional use and are applied either by hand equipment or machinery. Currently, the only products containing chlorpicrin that are applied to stored food commodities also contain methyl bromide, which is in the phase-out stage (except for quarantine uses). Data on currently registered products are available from the Australian Pesticides and Veterinary Medicines Authority.

Exposure: Public exposure is unlikely as residues are not allowed in food and are at the level of detection in cereal grains. It is also unlikely to be found in drinking water due to its physicochemical properties.

Since chloropicrin is highly soluble in water and has low adsorption in soil, it can potentially leach into groundwater and to surface water through run-off under a flooded condition. The low octanol/water partition coefficient of chloropicrin also indicates that it is not likely to be bioconcentrated in tissues of aquatic organisms (USEPA 2008).

A major route of exposure to chloropicrin is likely to be inhalation from gaseous sources, such as leaking and venting from fumigation chambers, and gas escape when using the product.

Typical values in Australian drinking water

No data are available on concentrations of chloropicrin in Australian drinking waters. Chloropicrin has been detected in drinking water supplies in the USA at concentrations of less than 0.005 mg/L (USEPA 1990) and in Korea at concentrations less than 0.003 mg/L (Lee et al. 2001).

Treatment of drinking water

There are no reports of the treatment of chloropicrin in drinking water.

However, given that chloropicrin may be formed in water as a chlorination disinfection by-product, the presence of chloropicrin in drinking water can be minimised by removing naturally occurring organic matter from the source water, by optimising disinfection practices, or by using alternative disinfectants. Most importantly, adequate disinfection must remain the primary concern and should not be compromised in response to a perceived need to lower levels of chloropicrin that may be detected.

Measurement

A solvent extraction procedure is suitable for the analysis of chloropicrin (USEPA method 551 1990). Sodium chloride is added to the sample, and the chloropicrin extracted using methyl tert-butyl ether. The extract is then analysed using gas chromatography with an electron capture detector. The limit of detection is approximately 20 ng/L. Other methods include purge and trap-gas chromatography-mass spectrometry, with detection limits reported as 250 ng/L (Lee et al. 2001).

History of the health values

No acceptable daily intake (ADI) or acute reference dose (ARfD) values have been established for chloropicrin.

The available toxicity data on chloropicrin have not been evaluated to establish a health value.

A health value has not been previously established by NHMRC.

Health considerations

Chloropicrin has had only limited toxicological assessment by Australian authorities. The Australian Government Department of Health and Ageing proposed chloropicrin for a review by the Australian Pesticides and Veterinary Medicines Authority in 2008, based on the absence of data to determine a safe level of exposure, especially to workers.

The United States Environmental Protection Agency (USEPA) selected a reversible acute endpoint using a human sensory irritation study with a benchmark concentration level ($\text{BMCL}_{10}$) of 0.073 parts per million (0.073 mg/L). At this level, the USEPA does not expect eye or nose irritation, upper respiratory changes, or any other health effects (USEPA 2008).

Poisons Schedule: Chloropicrin is included in Schedule 6 or 7 and Appendix J (Conditions for availability and use of Schedule 7 poisons) of the Standard for the Uniform Scheduling of Medicines and Poisons No.1, 2010 (the Poisons Standard)(DoHA 2010), depending on concentration Current versions of the Poisons Standard should be consulted for further information.

Derivation of the health-based guideline

As a no-observed-effect level (NOEL) for repeat exposure to chloropicrin has not been determined, it is not possible to determine a health-based guideline value for chloropicrin in drinking water.

The World Health Organization has not established a guideline value for chloropicrin because of inadequate data (WHO 2004).

References

NOTE: The toxicological information used in developing this fact sheet is from reports and data held by the Department of Health, Office of Chemical Safety.

DoHA (2010) The Poisons Standard; Schedule 1-Standard for the Uniform Scheduling of Medicines and Poisons, Department of Health and Ageing, Commonwealth of Australia, Canberra.

Lee JL, Kim BH, Hong JE, Pyo HS, Park S-J, Lee DW (2001). A study on the distribution of chlorination by-products (CBPs) in treated water in Korea. Water Research, 35(12):2861-2872.

Tomlin CD (ed) (2006). The Pesticide Manual: a world compendium, 14th Edition, British Crop Production Council, UK.

USEPA (United States Environmental Protection Agency) (1990). Draft Method 551: Determination of chlorination disinfection by-products and chlorinated solvents in drinking water by liquid-liquid extraction and gas chromatography with electron capture detection. USEPA, Environmental Monitoring and Support Laboratory (EMSL), Cincinnati, Ohio.

USEPA (United States Environmental Protection Agency) (2008). Office of Pesticide Programs RED Fact Sheet: Chloropicrin, 10th July 2008.

WHO (World Health Organization) (2004). Guidelines for Drinking-water Quality. 3rd Edition, WHO, Geneva, Switzerland.