7200

• UCREFRP Catalog Number: 7200
• Author: Odenkirchen, E. W. and R. Eisler.
• Title: Chlorpyrifos Hazards to Fish, Wildlife, and Invertebrates
• USFW Year: 1988.
• USFW - Doc Type: A Synoptic Review.
• Copyright Material: NO

ENVIRONMENTAL CHEMISTRY

Formulations of ch1orpyrifos include emulsifiable concentrates, wettable
powders, granules, pellets, microencapsulates and impregnated materials.
Suggested di1uents for concentrates include water and petroleum distillates,
such as kerosene and diesel oil. Carrier compounds include synthetic clays
with alkyl/aryl su1fonates as wetting agents (Table 1). Little information is
available to assess the influence of various use formulations on toxicity,
dispersal, decomposition, and bioavai1abi1ity. Chemical and other properties
of ch10rpyrifos are summarized in Table 2.

The degradation half-life time (Tb1) of ch10rpyrifos is 7.1 days in
seawater (Schimmel et a1. 1983), and 532days in distilled water (Freed et a1.
1979). Degradation is usually through hydrolysis to produce
3,5,6-trich10ro-2-pyridino1, and phosphorthioic acid (Brust 1966; Smith 1966,
1968; Marshall and Roberts 1978). Temperature, ~H, radiation, and metal
cations all significantly affect ch10rpyrifos Tb- in water: half-life is
decreased with increasing water pH, temperature', su~light, and metal cation
concentrations (Brust 1966; Mortland and Raman 1967; Smith 1968; Schaefer and
Dupras 1969, 1970; Meikle and Youngson 1970).

In soil, Tb1 values for ch1orpyrifos range from less than 1 week to
more than 24 w€eks, depending on soil moisture, microbial activity, clay and
organic content, and temperatu~e. In t11 soils studied, increasing
temperature resulted in decreased Tb- values (Miles et a1. 1983).
Degradation was more rapid in sandy loam th&n in organic muck soils, more
rapid in moist than in dry soils, and more rapid in clay than in other soil
types (Getzin 1981; Miles et a1. 1983, 1984). The major routes of
ch1orpyrifos loss from soils are chemical hydrolysis in moist soils,
clay-catalyzed hydrolysis in dry soils, and microbial degradation and
volatilization (Marshall and Roberts 1978).

The half-life of ch10rpyrifos in sediments is comparatively long; it was
24 days in a sediment-water slurry (Schimmel et a1. 1983). In a pond treated
with ch10rpyrifos, total waterborne residues decreased by a factor of more
than lOX, while total sediment residues rose by about 3X (Hurlbert et a1.
1970). Similar results were noted in an artificial lake treated with
chlorpyrifos: lake water concentrations peaked 1 day after treatment at 0.9
Jg/1 and plateaued near 0.2 ug/l after 3 weeks (Mu11a et a1. 1973).

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