Microsomal activation of chlordane isomers to derivatives that irreversibly interact with cellular macromolecules

Maternal and Paternal Household Pesticide Exposure During Pregnancy and Risk of Childhood Acute Lymphoblastic Leukemia

OBJECTIVE

The aim of this study was to investigate whether risk estimates for childhood acute lymphoblastic leukemia change when restricting model comparison groups to "nonpesticide exposure" (NPE10) households.

METHODS

Cases ( n = 1810) 15 years or younger were identified through Children's Cancer Group institutions between 1989 and 1993 and age-/sex-matched to controls ( n = 1951). Household pesticide use during pregnancy/month prior was collected via telephone. NPE10 comparison group reporting no parental exposure to 10 pesticide classes was identified.

RESULTS

Adjusted odds ratios increased from 15% to 49% when limiting the comparison to NPE10. Maternal termite insecticide exposure was associated with greatest risk (adjusted odds ratio, 4.21; 95% confidence interval, 2.00-8.88). There was minimal evidence of interaction by child sex or occupational pesticide exposure, and no monotonic dose-response pattern with frequency of use (times per year).

CONCLUSIONS

Elevated risks are consistent with published pooled-/meta-analyses and DNA damage. The consistency and magnitude of these associations warrant product labeling, exposure reduction interventions, or both.

Direct suppression of cultured spleen cell responses by chlordane and the basis for differential effects on in vivo and in vitro immunocompetence

Immunosuppression by gamma-chlordane was examined by the direct addition of chlordane to cultured spleen cells from untreated B6C3F1 mice. Both cell-mediated and humoral immune responses were markedly suppressed upon in vitro exposure. The mixed lymphocyte response and the proliferative response to both B- and T-cell mitogens were significantly suppressed at micromolar concentrations of chlordane. The antibody response to sheep erythrocytes (SRBC) was suppressed 90% at 10 microM chlordane. The kinetics of the SRBC response were not altered by chlordane. Addition of chlordane to the antibody cultures on various days indicated an effect at the early stages of the response. Previous studies with chlordane failed to demonstrate immunosuppression following in vivo exposure. The possibility that chlordane was metabolized in vivo to a less immunosuppressive form was studied by examining the effect of the major metabolite, oxychlordane, on the in vitro antibody response and by incubating splenocytes with chlordane and a liver S9 preparation prior to culture with SRBC. Oxychlordane was immunosuppressive by itself, and the activity of chlordane was unaltered in the co-culture experiments. The association of chlordane with serum components was evaluated in vitro in cultures of mouse bone-marrow cells (BMC). The chlordane-induced suppression of [3H]thymidine incorporation by BMC was reversed by the addition of mouse or human serum. In summary, chlordane produces marked suppression of in vitro immune responses via an apparent antiproliferative action. The failure of chlordane to produce in vivo immunosuppression may be related to extensive association of chlordane with serum components.

Development of safer insecticides

In summary, it might be said that there is no simple answer to the problems inherent in the search for safer insecticides by rational methods. However, the subject has not yet been fully explored and opportunities remain for exploitation. The extent to which this is done will depend on more effective use of time, scientific manpower, and imagination.