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

MALATHION 97
3. HEALTH EFFECTS
with malathion 6 days after the second sensitization (Cushman and Street 1983). The findings of Rodgers
and Xiong (1997b) and Cushman and Street (1983) are listed in Table 3-3. An additional study examined
the effects of a malathion dip preparation on selected immunologic parameters in BALB/c mice (Relford
et al. 1989). Mice were briefly submersed in a solution of 2 or 8% malathion twice with a 10-day interval
in between doses. The cellular immune response was assessed by in vitro exposure of lymphocytes to
mitogens, whereas the humoral response was measured by quantifying antibody production against
SRBC. Sampling started 3 days after the second treatment and continued at 6-day intervals for a total of
5 samplings. Treatment with malathion did not significantly alter the cellular immune response to
mitogens (Concanavalin A, phytohemagglutinin, pokeweed mitogen, lipopolysaccharide), with the
exception of a suppressed B cell response to LPS on day 3 in both treated groups. This suppression was
not seen at other sampling times. Responses to the SRBC were no different among control and treated
groups. No exposure level could be estimated in this study.
3.2.3.4 Neurological Effects
A case of dermal poisoning with malathion was described by Parker and Chattin (1955). The victim was
a 10-year-old girl who had extensive dermal contact with a commercial malathion formulation in the form
of flakes and became semi-comatose 48 hours after exposure. On admission, there was stiffness of the
neck and back and there were signs of meningeal irritation; deep reflexes of the lower extremities were
absent. Following treatment with atropine, there was gradual recovery towards normality. Cholinesterase
levels were measured in two studies that had significant dermal exposure to malathion. Ramu et al.
(1973) described several cases of intoxication in children following a hair wash with a solution containing
50% malathion in xylene. In four severely intoxicated children, serum cholinesterase levels increased
from undetected on admission to almost within the normal range 72 hours later, after appropriate
treatment for organophosphate poisoning. Baker et al. (1978) measured RBC cholinesterase activity in
occupationally exposed subjects at the beginning and end of the day during the period of pesticide use.
The percent decreases varied by pesticide formulation; in mixers and spraymen, the average decrease
from morning to evening (after a day of exposure) was about 40–45% with a formulation that contained
the lowest concentration of malathion and the highest concentration of four breakdown products,
including isomalathion.
Few studies were available providing information on neurological effects of malathion following dermal
exposure of animals. Lethargy and anorexia were described in mice following a brief submersion in a dip
preparation of 2 or 8% malathion (Relford et al. 1989). Vestweber and Kruckenberg (1972) studied the