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

MALATHION 33
3. HEALTH EFFECTS
(Hermanowicz and Kossman 1984). As noted in Section 3.2.1.2, the frequency of upper respiratory tract
infections was greater in workers than in controls. The role of malathion, if any, in the observed effects
cannot be determined.
The study by Kahn et al. (1992) in Santa Clara County, California, described above (Respiratory Effects),
showed that there were no significant increases in the number of visits for the broad category, allergic
problems, to hospital emergency departments during the application period compared with the prespray
period or the corresponding period the previous year. The results of the surveys to assess self-reported
symptoms revealed no detectable increase in acute morbidity or in organophosphate-compatible
symptomatology, although the sample size may have been too small to detect small increases in
prevalence of various symptoms.
No studies were located regarding immunological effects in animals following inhalation exposure to
malathion.
3.2.1.4 Neurological Effects
Numerous studies were located that provided information on the neurological effects of exposure by
humans to organophosphate pesticides in the air, but few evaluated exposure specifically to malathion,
and provided quantitative exposure data. End points evaluated included measurements of red blood cell
(RBC) and plasma cholinesterase activity as well as measurements of neurophysiological parameters and
clinical signs. Most studies evaluated workers exposed repeatedly over periods of time ranging from
weeks to years.
Effects on Cholinesterase Activity. In a controlled-exposure study, 16 male volunteers (4/exposure level)
were exposed to aerosol bombs that contained 0 (control), 5, or 20% actual malathion 1 hour 2 times/day
for 42 days (Golz 1959). The actual exposure concentrations were 0, 5.3, 21, or 85 mg/m 3 . The
malathion in the formulation was 95% pure. There were no signs of toxicity during the study and no
significant effect on either plasma or RBC cholinesterase activity. Similar lack of effects on plasma and
RBC cholinesterase was reported by Culver et al. (1956) among a group of men exposed outdoors for
4–5 hours to malathion concentrations between 0.5 and 4 mg/m 3 , with peak concentration of up to
56 mg/m 3 .