Changes in T-lymphocyte distribution associated with ingestion of aldicarb-contaminated drinking water: a follow-up study.

The carbamate pesticide, aldicarb, is the most commonly found man-made groundwater contaminant in Wisconsin. A 1985 study linked ingestion of aldicarb-contaminated drinking water with altered T-cell distributions, specifically an increase in the mean number of CD8+ (T8) T cells. To further evaluate this finding, a follow-up study was done in 1987. Of the 50 Portage County, Wisconsin, women who participated in the first study, 45 participated in the follow-up: 18 formerly exposed and 27 formerly unexposed. In our follow-up study, only 5 women were found to be currently exposed to aldicarb. This group of 5 women, compared to 39 unexposed women who had peripheral blood specimens taken, had an increased percentage of lymphocytes and an increased number of CD2+ T cells, due to an increased number of total CD8+ T cells. Although the number of exposed persons was small, the increases in percentage lymphocytes and absolute numbers of CD2+ and CD8+ T cells were consistent with a dose-response relationship. No identified drinking water contaminant other than aldicarb could explain these findings. These results support earlier evidence linking aldicarb exposure and lymphocyte distribution changes. Although adverse clinical effects have not been documented, the widespread use of this chemical and consequent potential for widespread exposure indicate a clear need for further research on this issue.