toxicological profile for malathion - Agency for Toxic Substances and ...

MALATHION 90
3. HEALTH EFFECTS
suggested by the study authors as being the primary route of exposure. However, the reader should keep
in mind that considerable dermal absorption may have also occurred in many studies summarized in
Section 3.2.1.
3.2.3.1 Death
A large study of 7,500 workers in 1976 in Pakistan who sprayed various malathion formulations reported
that at least five workers (two mixers and three sprayers) died, probably as a result of exposure to the
pesticide (Baker et al. 1978). Poor work practices (e.g., wearing clothing soaked with pesticide for
several days without washing, mixing chemicals with bare hands) resulted in excessive skin contact and
absorption of the pesticide through the skin. Baker et al. (1978) estimated that the daily dermal exposure
for the spraymen was 330 mg of malathion. Isomalathion, an inhibitor of carboxylesterase and therefore a
synergist for malathion, was suspected to be a major contributor in the toxicity of at least two of three
formulations used. Ramu et al. (1973) reported the death of a 9-year-old child 5 days after exposure to
malathion through a hair wash containing 50% malathion in xylene. No other studies describing death
specifically linked to dermal exposure were found.
A dermal LD50 of >4,444 mg/kg was reported in Sherman rats for malathion (Gaines 1960). Application
of a single dose of 4,444 mg/kg of a 57% emulsifiable concentrate of malathion in xylene to a clipped
area of the back resulted in the death of 4 out of 10 males within 1 hour of dosing (Gaines 1960, 1969).
The only additional information available regarding dermal lethality is from a 30-day intermediateduration
study in male guinea pigs in which application of 200 mg/kg/day of malathion (98% pure) in
acetone to a 36 cm 2 clipped area of the skin killed 4 out of 10 animals during days 20–30 (Dikshith et al.
1987). Signs of toxicity before dying included tremors, dyspnea, salivation, convulsions, and paralysis of
the hind limbs. The lethality values from these two studies are presented in Table 3-3.
3.2.3.2 Systemic Effects
The highest NOAEL values and all reliable LOAEL values for systemic effects in each species and
duration category are recorded in Table 3-3. No studies were located regarding cardiovascular,
gastrointestinal, or musculoskeletal effects in humans or animals following dermal exposure to malathion.