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Chlorpyrifos-ethyl (Figure 24) is one of the most widely used insecticides of about 100
manmade organophosphate insecticides. The substance is marketed under the trade
names Dursban and Lorsban (pan-uk, 2005). It is used as a broad-spectrum insecticide
for the treatment of grain, cotton and vegetable crops (Extoxnet Information About
Chlorpyrifos, 1993). The compound was introduced in 1965 (Hayes, 1990) and is
produced mainly by Dow AgroSciences (Indianapolis, USA). European manufacturers
are Frunol (Unna, Germany) and Point Enterprises (Switzerland). About 1000 t is used
annually in Europe (pan-uk, 2005).
Key physico-chemical properties determining the environmental behaviour of
chlorpyrifos-ethyl and -methyl are listed in Table 51. The log K ow value of 4.7 - 5.3
indicates an affinity of chlorpyrifos-ethyl to accumulate in sediments and tissues of
marine organisms.
Table 51 Physico-chemical properties of chlorpyrifos-ethyl and -methyl.
Chlorpyrifos-ethyl
Chlorpyrif os-methyl
TCP
CAS number
2921-88-2
5598-13-0
6515-38-4
Log K ow
4.7 (23 °C)-5.27 a ' e
4.3 e
1.8 d
LogKoc [L/kg]
3.6-4.5 a ' b
Solubility in water [mg/L]
2 (25°C) b
4 f
220 d
Vapour pressure [Pa]
1.87xl0" 3 (25°C) a ' b
4.2x10-5 (25°C) f
2.68xl0" 5 (25°C) d
Atmospheric OH rate
constant [cm 3 /molecule s]
9.17xl0" n (25°C) c
Biodegradation
> month b
Log Kow: n-octanol-water partition coefficient, log KOC: soil-water partition coefficient
Data from: “(Extoxnet Information about Chlorpyrifos, 1993), b (Barrett et al., 2000),
c (www.chemindustrv.de). d (Watson, 2002), “(Noble, 1993), f (www.inchem.org)
Chlorpyrifos-ethyl exhibits a high acute toxicity for mammals via inhalation or
ingestion routes (LD50 value = 135 mg/kg bodyweight rat (Rornpp, 1995)). For fish,
aquatic invertebrates and other marine organisms, chlorpyrifos is highly toxic:
cholinesterase inhibition was observed in acute toxicity tests of fish exposed to very low
concentrations. The following publications give an overview of the effects on aquatic
organisms: (Extoxnet Information about Chlorpyrifos, 1993), (datasheet on
