Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:6:p1
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 6 (pt 1/6)
Character Range: 2649759–2652788

6                   Chlorpyrifos

6.1              General
Several reviews of chlorpyrifos in the environment and its toxicity to humans are available and should be consulted for more detailed information not presented in this summary (ATSDR 1997; WHO 2004; NRAAVC 2000; APVMA 2009; Taylor & Di Marco 2003). The following provides a summary of the key aspects of chlorpyrifos that are relevant to the derivation of a soil HIL.

Chlorpyrifos is the common name for the organophosphorous insecticide O,O-diethyl O-3,5,6-trichloro-2-pyridyl phophorothioate. Pure chlorpyrifos is an odourless, white to colourless crystalline solid. The compound is non-polar and therefore has a low solubility in water and an affinity for organic substances. It is also thermally sensitive at temperatures over 50 °C and decomposes at 130 °C (NRAAVC 2000; WHO 2004).

Technical grade chlorpyrifos has a minimum purity of 940 to 990 g/kg. It is a white to light yellowish brown crystalline solid with a mild mercaptan odour. Commercial formulations of chlorpyrifos are generally produced as a concentrated emulsion, liquid, wettable powder, dust, solid bait or granules (NRAAVC 2000).

Chlorpyrifos has been widely used in the Australian agricultural industry since the mid-1960s as it is reportedly less harmful to beneficial insects and is a useful tool in insecticide resistance management programs (NRAAVC 2000). It is used to control insects in soil and on crop foliage including fruit (pome, stone and citrus fruit, strawberries, figs, pineapples, kiwifruit and bananas), nuts, vines, vegetables (potatoes, asparagus), grains (rice, cereals, maize, sorghum), cotton, mushrooms, sugar cane, turf and ornamental plants (NRAAVC 2000). In industrial/commercial and domestic buildings chlorpyrifos is used to control termites, cockroaches, spiders, ants, mosquitoes and fleas and is generally sprayed in the sub-floor region during construction or applied around the building. It is also registered for use in dog and cat flea collars, sprays and shampoos. While the number of products containing chlorpyrifos changes on a yearly basis[1], in 2000 there were 164 products registered in Australia that contained chlorpyrifos (NRAAVC 2000).

In contrast to Australia, the US banned all domestic use of chlorpyrifos in 2001.

Chlorpyrifos is persistent in the environment with a half-life in soil reported to range from 3356 days for soil-incorporated applications (Tomlin 2003) to 462 days in Australian soil under conditions similar to the application of products on soil for termite control (Baskaran et al. 1999).

6.2              Previous HIL
No previous HIL is available for chlorpyrifos (NEPC 1999). It is noted, however that review of chlorpyrifos by Taylor & Di Marco (2003) derived a health-based soil investigation level (residential) of 80 mg/kg on the basis of a threshold toxicity reference value of 0.003 mg/kg/day (noted to be derived from US EPA), 100% oral bioavailability, soil ingestion only, and an assumption that exposures from