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

SUMMARY

Chlorpyrifos (phosphorothioic acid 0, O,-diethyl 0-(3,5,6,-trichloro-2-
pyridinyl) ester), an organophosphorus compound with an anticholinesterase
mode of action, is used extensively in a variety of formulations to control a
broad spectrum of agricultural and other pestiferous insects. Domestic use of
chlorpyrifos in 1982 was about 3.6 million kg; the compound is used mostly in
agriculture, but also to control mosquitos in wetlands (0.15 million kg
applied to about 600,000 ha) and turf-destroying insects on golf courses (0.04
mill ion kg).

Accidental or careless applications of chlorpyrifos have resulted in the
death of many species of nontarget organisms such as fish, aquatic
invertebrates, birds, and humans. Applications at recommended rates of 0.028
to 0.056 kg/surface ha for mosquito control have produced mortality,
bioaccumulation, and deleterious sublethal effects in aquatic plants,
zooplankton, insects, rotifers, crustaceans, waterfowl, and fish; adverse
effects were also noted in bordering invertebrate populations.

Degradation rate of chloropyrifos in abiotic substrates varies, ranging
from about 1 week in seawater (50% degradation) to more than 24 weeks in soils
under conditions of dryness, low temperatures, reduced microbial activity, and
low organic content; intermediate degradation rates reported have been 3.4
weeks for sediments and 7.6 weeks for distilled water. In biological samples,
degradation time is comparatively short--usually less than 9 hours in fishes,
and probably the same in birds and invertebrates.

Chlorpyrifos is acutely toxic to some species of aquatic invertebrates
and teleosts at nominal water concentrations ranging between 0.035 and 1.1
ug/l. Acute single-dose oral LD-50 values of chlorpyrifos to susceptible
avian species ranged from 5 to 13 mg/kg body weight. Mammals were
comparatively tolerant of chlorpyrifos: acute oral LD-50's were reported to be
151 mg/kg body weight, and higher. Lethal dietary concentrations for
sensitive species of birds ranged from 30 to 50 mg chlorpyrifos/kg food.
Sublethal effects were recorded in all species of organisms examined at
concentrations below those causing mortality. These effects included
bioconcentration from the medium by teleosts (410X to 1,000X); cholinesterase
activity reduction in brain and hematopoietic tissues; reduced growth;
impaired reproduction, including sterility and developmental abnormalities;

i i i