Date of Degree
PhD (Doctor of Philosophy)
Paul A. Romitti
Hypospadias is a congenital malformation that occurs in 0.3-1% of live births, in which the meatus (the urethral opening) is dorsally malpositioned. Uncorrected hypospadias can cause difficulties in urination, abnormal sexual function, and adverse psychological consequences; surgical correction, though generally successful, constitutes an economic burden for families. Several common classes of pesticides have demonstrated potential to disrupt normal endocrine hormones that regulate fetal genitourinary development. Past epidemiologic studies of pesticide exposure and risk of hypospadias have been limited by limited available data, small sample sizes, or poor ascertainment of pesticide exposure.
The objective of this study was to examine the relationship between parental occupational pesticide exposure and risk of hypospadias in their offspring; and further, to assess whether addition of residential pesticide exposure data is feasible and contributes to overall pesticide exposure. We began by conducting a meta-analysis of the current literature, in which summary measures of occupation (such as census occupation code) had been used to assign pesticide exposure. We found elevated but marginally significant risks of hypospadias were associated with maternal occupational exposure (PRR of 1.36, CI = 1.04-1.77), and paternal occupational exposure (PRR of 1.19, CI= 1.00-1.41) in the previously published literature.
We then used industrial hygienist review of occupational histories to estimate the relationship between pesticide exposure and risk of hypospadias. We found that maternal occupational exposure to any pesticides (yes/no) was not associated with an increased risk of hypospadias (OR = 0.83, 95% CI = 0.6-1.1), cumulative insecticide (OR = 1.09; 95% CI = 0.9- 1.3), herbicide (OR = 1.05; 95% CI = 0.9- 1.2), or fungicide (OR = 0.91; 95% CI = 0.7-1.2) exposure. These negative findings might be explained by a lack of relationship at the low levels of exposure observed in this study population, in which case another farm exposure could be related to hypospadias; or this negative finding may be due to exposure misclassification.
Finally, we evaluated the feasibility and relevance of collecting residential pesticide exposure and direct reports of occupational exposure from fathers. Residential pesticide use during the six months prior to pregnancy and during pregnancy was common among control mothers: 45% reported that their home had been treated for insect or rodent pests; 47% reported that their lawn or garden had been treated for weeds or insect pests; 16% used a lawn service; 26% reported that a pet had been treated for fleas, ticks, or mites (including flea and tick preventives); 17% reported community-wide sprayings for pests; and 16% reported that their workplaces were treated for pests. Case mothers were more likely to report that their home had been treated of insect or rodent pests (50%) or that a pet had been treated for fleas, ticks, or mites (36.5%). Our results suggest that collection of information on residential pesticide use is feasible, and the impact of residential pesticide use on birth defects risk should be assessed in future studies.
Copyright 2009 Carissa Marie Rocheleau
Rocheleau, Carissa Marie. "Pesticide exposure and risk of hypospadias: assessment and the adequacy of exposure measurements." dissertation, University of Iowa, 2009.