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

MALATHION 36
3. HEALTH EFFECTS
Francisco Bay area (Thomas et al. 1992). Using several measures of malathion exposure and adjustment
for confounders, the study found no significant association between exposure to malathion and
spontaneous abortion. There was a moderate association between stillbirths and exposure accumulated up
to 1 month before death. The one major weakness of the study is possible exposure misclassification,
based on using residence as the surrogate for exposure, although the authors felt that this seemed much
less vulnerable to recall bias than would a subject’s recollection of whether or not she had been exposed
(Thomas et al. 1992). Rupa et al. (1991b) investigated reproductive outcomes in 1,016 couples in which
the males’ main jobs were mixing and spraying pesticides (including malathion and also organochlorine
pesticides) compared with 1,020 unexposed couples, and found significantly higher percent ages of
stillbirths (8.73 versus 2.65%) and abortions (26.0 versus 15.0%) in exposed workers. A significantly
lower percent of fertile males (80.8 versus 94.9% in controls) and decreased frequency of live births
(53.0 versus 80.1%) was also observed. Rupa et al. (1991b) further stated that 80% of the males in the
exposed group showed ill effects such as severe giddiness, and nervous, skin, and eye disorders. The role
of malathion in these findings, if any, cannot be determined.
No studies were located regarding reproductive effects in animals following inhalation exposure to
malathion.
3.2.1.6 Developmental Effects
Three studies were located that examined the association between developmental outcomes and exposure
to malathion, with varying outcomes. Grether et al. (1987) examined occurrence of defects and low birth
weight using newborn hospital discharge data and vital records in the San Francisco Bay area after aerial
malathion spraying. The study included an exposed cohort of 24,987 births and an unexposed cohort of
15,278 births. Although the authors found some positive (and significant) associations for some
anomalies, the anomalies that occurred more frequently than expected did not represent a biologically
consistent pattern. No significant association was found between low birth weight and increasing
exposure to malathion. Thomas et al. (1992) (described above in Section 3.2.1.5) found a statistically
significant association between incidence of gastrointestinal anomalies in offspring and exposure to
malathion during the second trimester of pregnancy (odds ratio [OR]=4.14; CI=1.01, 16.6). No
significant associations were observed for intrauterine growth retardation or other congenital effects
reportable by the California Birth Defects Monitoring Program. García et al. (1998) compared paternal
pesticide exposures between offspring with congenital malformations (i.e., nervous system and
cardiovascular defects, oral clefts, epispadia or hypospadias, musculoskeletal defects, unspecified defects)