1,3-Dichloropropene
(endorsed 2011)
Guideline
Based on human health concerns, 1,3-dichloropropene in drinking water should not exceed 0.1 mg/L.
Related chemicals
1,3-Dichloropropene (CAS 542-75-6) does not belong to a recognised class of chemicals. The commercial product is a mixture of the cis and trans isomers (Tomlin 2006).
Human risk statement
With good water quality management practices, exposure of the general population is expected to be well below levels that may cause health concerns.
If present in drinking water as a result of a spillage or through misuse, 1,3-dichloropropene would not be a health concern unless the concentration exceeded 0.1 mg/L. Excursions above this level would need to occur over a significant period to be a health concern, as the health-based guideline is based on long-term effects.
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: 1,3-Dichloropropene is a nematocide for the control of soil pests including plant parasitic nematodes.
There are registered products that contain 1,3-dichloropropene in Australia. These products are intended for professional use only by authorised or licensed persons as a pre-plant soil fumigant. 1,3-Dichloropropene is available as a concentrated solution to be applied in undiluted form using soil injection equipment, or in diluted form by drip irrigation, and applied as either a broadacre or row soil treatment. Data on currently registered products are available from the Australian Pesticides and Veterinary Medicines Authority.
Exposure sources: The main source of public exposure to 1,3-dichloropropene is contamination of water. No residues are expected in food.
Agricultural use of 1,3-dichloropropene may potentially lead to contamination of source waters through absorption into the soil moisture and subsequent leaching into groundwater.
Typical values in Australian drinking water
No reports of 1,3-dichloropropene in Australian drinking waters have been identified. However, laboratory experiments indicate that leaching 1,3-dichloropropene residues through soil to water is likely to be significant (Guo et al. 2003). Therefore there is some risk of contamination of groundwaters in areas where 1,3-dichloropropene is applied to agricultural soils.
Treatment of drinking water
No reports have been identified for the targeted treatment of 1,3-dichloropropene in drinking water supplies.
Measurement
Analysis of 1,3-dichloropropene by solid-phase micro-extraction followed by gas chromatography with electron capture detection has been reported, with a limit of quantitation of 0.5 mg/L (Fuster et al. 2005). Further optimisation of this approach has been reported to achieve method detection limits of 0.5 ng/L for cis-1,3-dichloropropene and 1.0 ng/L for trans-1,3-dichloropropene (Antelo et al. 2007). An on-line purge and trap gas chromatography mass spectrometry has been developed with a reported limit of quantitation of 0.1 mg/L (Frenich et al. 2009).
History of the health values
Currently no acceptable daily intake (ADI) or acute reference dose (ARfD) values have been established for 1,3-dichloropropene, since these are required only for pesticides with residues in food. There are no detectable residues in crops when 1,3-dichloropropene is used as a pre-plant soil fumigant.
A health value has not previously been established by NHMRC.
Health considerations
Metabolism: 1,3-dichloropropene is readily and extensively absorbed via the gastrointestinal tract in rats. It is extensively metabolised, and the metabolites are rapidly excreted in the urine, almost completely within 48 hours. The primary metabolite of 1,3-dichloropropene in the urine is N-acetyl-S-(3-chloroprop-2-enyl)cysteine.
Acute effects: 1,3-dichloropropene (both the cis isomer and a mixture of the cis and trans isomers) has moderate acute oral and dermal toxicity in rats, and is a skin sensitiser in guinea pigs.
Short-term effects: Short-term studies in mice and rats reported reduced bodyweight gain, decreased clinical chemistry parameters, hyperplasia of the gastric mucosa and decreased organ weights at 15 and 5 mg per kg body weight per day (mg/kg bw/day), respectively. At higher doses in mice, there was decreased vacuolation of the renal tubules at 175 mg/kg bw/day. In a short-term study in dogs, vomiting occurred at 10 mg/kg bw/day. The lowest overall no-observed-effect level (NOEL) was 3 mg/kg bw/day in rats.
Long-term effects: Two-year dietary studies in mice and rats reported reduced bodyweight gain, decreased serum triglycerides and decreased organ weights at 25 mg/kg bw/day and 12.5 mg/kg bw/day respectively. In rats, there was also an increased incidence of liver adenomas and hyperplasia of the gastric mucosa at 12.5 mg/kg bw/day. A 1-year dietary study in dogs reported anaemia, with increased haematopoiesis from 15 mg/kg bw/day. The lowest NOEL was 2.5 mg/kg bw/day in rats, mice and dogs.
Carcinogenicity: Tumour formation was observed in long-term studies in mice and rats. In rats, there was an increase in primary hepatocellular adenomas at 12.5 mg/kg bw/day, and squamous cell papillomas and some carcinomas of the forestomach at 50 mg/kg bw/day. In mice, there was an increase in bladder and lung tumours at 50 mg/kg bw/day. These effects occurred at doses well in excess of the likely level of human exposure through drinking water. In male mice exposed via inhalation to 60 ppm technical-grade 1,3-dichloropropene for 24 months, an increased incidence of bronchioalveolar adenomas was seen.
Genotoxicity: 1,3-dichloropropene was positive in some in vitro short-term assays but negative in most in vivo assays. Overall, it was not considered to be genotoxic.
Reproductive and developmental effects: Reproduction studies and developmental toxicity studies via the inhalation route in rats and rabbits did not produce any evidence of effects on reproductive parameters or foetal development. No dietary studies were available.
Poisons Schedule: 1,3-dichloropropene is included in Schedule 7 of the Standard for the Uniform Scheduling of Medicines and Poisons No.1, 2010 (the Poisons Standard)(DoHA 2010), with an Appendix J rider limiting availability to authorised or licensed persons. Current versions of the Poisons Standard should be consulted for further information.
Derivation of the health-based guideline
The health-based guideline of 0.1 mg/L for 1,3-dichloropropene was determined as follows:
where:
2.5 mg/kg bw/day is the NOEL based on long-term (1- and 2-year) studies in rats, mice and dogs.
70 kg is taken as the average weight of an adult.
The proportionality factor is 1, since 1,3-dichoropropene has no residues in food and therefore the assumption is that 100% of the ADI (nominal in this case) will arise from the consumption of drinking water.
2 L/day is the estimated maximum amount of water consumed by an adult.
1000 is the safety factor applied to the NOEL derived from animal studies. This safety factor incorporates a factor of 10 for interspecies extrapolation, 10 for intraspecies variation and an additional 10 for the uncertainty associated with the potential carcinogenic risk.
The World Health Organization has established a health-based guideline value of 0.02 mg/L for 1,3-dichloropropene in 1993 (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.
Antelo A, Lasa M, Millan E (2007). Use of experimental design to develop a method for analysis of 1,3-dichloropropene isomers in water by HS-SPME and GC-ECD. Chromatographia, 66(7-8): 555-563.
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.
Frenich AG, Aguado SC, Vidal JLM, Arrebola FJ (2009). On-line purge and trap GC-MS for monitoring 1,3-dichloropropene in agricultural water and soil samples. Journal of Chromatographic Science, 47(1): 26-30.
Fuster S, Beltran J, Lopez FJ, Hernandez F (2005). Application of solid phase microextraction for the determination of soil fumigants in water and soil samples. Journal of Separation Science, 28(1):98-103.
Guo MX, Yates SR, Zheng W, Papiernik SK (2003). Leaching potential of persistent soil fumigant residues. Environmental Science & Technology, 37(22):5181-5185.
Tomlin CD (ed) (2006). The Pesticide Manual: a world compendium, 14th Edition, British Crop Production Council, UK.
WHO (World Health Organization) (2004). Guidelines for Drinking-water Quality, 3rd Edition. WHO, Geneva, Switzerland.
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