Nonpersistent Pesticides Found in Umbilical Cord Blood


(Beyond Pesticides, June 17, 2010)

Researchers have found detectable levels of common household pesticides in the majority of umbilical cord blood of babies born at an urban hospital. The study looks at concentrations of organophosphate (OP), carbamate, pyrethroids, and organochlorine pesticides in samples of umbilical cord blood taken from newborns delivered at the Johns Hopkins Hospital Labor and Delivery Suite in Baltimore. Researchers looked at the umbilical cord serum, as opposed to maternal serum, in order to provide a more direct estimate of exposure to the fetus. While human biomonitoring studies have found detectable levels of these pesticide chemicals in urine and blood samples from children and adults in the past, few studies have been carried out in the U.S. evaluating exposure in utero.

In addition to tracking pesticide concentrations, researchers also aimed to identify demographic and socioeconomics factors associated with in utero pesticide exposure. Anonymous anthropometric and sociodemographic characteristics of the mothers and infants were collected along with umbilical cord blood that would have otherwise been discarded. Included in the characteristics collected that researchers considered might affect pesticide exposure risk were: age, race, body mass index, parity, education, health insurance, marital status, smoking, area of residence and housing density.

There were a total of 591 live singular births between November 26, 2004 and March 16, 2005, of which 300 were used for chemical laboratory analysis for this study. Of these, 297 samples were successfully analyzed for organochlorine pesticides, and 185 were successfully analyzed for pesticides that are traditionally thought of as being “nonpersistent” with half-lives ranging from hours to weeks.

Using principal component analysis, a statistical method to identify pesticides and metabolites that tend to appear together, the authors found that newborns rarely received exposure to both permethrin and carbamates. Permethrin levels were higher among infants of mothers who did not complete high school compared with women with at least a high-school education, possibly suggesting that less educated women live in environments with greater pest problems. Highly educated mothers, on the other hand, had babies with higher cord serum concentrations of DDT mixtures, suggesting an association between higher education or socioeconomic status with high consumption of foods containing levels of DDT, such as fish.

Of the persistent pesticides, the parent compound p,p’-DDT and its metabolite, p,p’-DDE were detected in 90% and 100% of serum samples, respectively. Hexachlorobenzene was detected in 98%, and two chlordane-related chemicals (trans-nonachlor and oxychlordane) were detected in 93% and 84% respectively.

Researchers considered the carbamate, pyrethroids and OP pesticides to be the nonpersistent pesticides. Results of the study found that among the carbamate pesticides, bendiocarb was detected in 73% of the samples and propoxur was detected in 55%. Permethrin isomers (cis– and trans-permethrin) were detected in 41% and 52% respectively, and piperonyl butoxide (PBO) was detected in 36%. Cyfluthrin was found in only four samples. For OP pesticides, chlorpyrifos was detected in five of the samples and diazonin was not detected in any. Because scientists think that these pesticides disappear from the human body within a few days, the study suggests that the pregnant women either received regular, chronic exposure, which may cause fetal development problems, or that they were exposed shortly before childbirth, perhaps even in the hospital, the authors speculate.

“We can see that they’ve been exposed, but we don’t know if there are health consequences,” says first author Gila Neta, an epidemiologist who is now at the National Cancer Institute.

While the study measured pesticide levels in the umbilical cord blood, there was no information on pesticide-use behaviors as some other studies have done. However, though the study was very narrowly focused, it provides a valuable case for the need for further assessment of exposure to pesticides, particularly in vulnerable populations such as pregnant women. Furthermore, because this study only sampled newborns in one urban area, results might be higher in other areas, such as agricultural and rural regions where exposure is increased.

According to Donald Wigle, Ph.D., an epidemiologist at McLaughlin Centre for Population Health Risk Assessment at the University of Ottawa, the results point to important questions that could be resolved by the National Children’s Study. The study, among many other goals, plans to look at pesticide exposure patterns and their possible effects on pregnancy and child health.

Results of this study, “Distribution and Determinants of Pesticide Mixtures in Cord Serum Using Principal Component Analysis” can be found online in the journal Environmental Science & Technology.

Source: Chemical and Engineering News