“Organochloride compounds (OC) and fetal development”


Organochloride compounds (OC) are chemicals that can naturally occurre, but mostly come from human activity. These compounds are chemically extremely stable; therefore they can persist in the environment long after the compounds had been used. As a consequence of the chemicals’ attractiveness to fat, these compounds remain for long periods of time accumulated in animal and human fatty tissue. OC include dichlorodiphenyltrichloroethane (DDT), widely used as pesticide and polychlorinated-biphenils (PCBs), mainly used in electrical transformers, plastic, paint, and rubber products. These compounds are banned in most of the developed countries since the 70’s and 80’s. However, in countries with endemic malaria the use of DDTs is still not prohibited.

In animal studies, exposure to OCs has been linked to various adverse effects on the developing fetus, such as effects on the nerve, endocrine, immunologic, and reproductive system. Findings related to accidentally high level OCs’ exposure amongst humans are consistent with the results of the animal studies. However, the results related to low-levels of exposure are inconsistent, and difficult to compare because of the heterogeneity between studies.

In this study, the investigators analyzed the potential health effects of prenatal exposure to one PCB type, PCB-153, and one of the metabolites of DDT, known as DDE. Particularly, the study focused on the effects of these compounds on birth outcomes, such as the length of the pregnancy and the birth weight of newborns. They included more than 9000 mother-child pairs from European birth cohort studies like the INMA project. The investigators measured the levels of PCB-153 and DDE in maternal blood and breast milk and they the levels of these compounds in the umbilical cord blood of the newborn. They found that newborns with higher umbilical cord blood PCB-153 levels tended to be born with lower birth weight than babies with lower level of umbilical cord blood PCB-153. This association was stronger amongst babies whose mother had been smoking during pregnancy, or belong ethnicities to other than Caucasian. The investigators could not find any association between prenatal exposure to PCB-153 and DDE and the length of the pregnancy.

Overall, the investigators emphasized that prenatal exposure to PCB-153 can influence the growth of the developing baby and that this effect can be strengthened by other exposures occurring during pregnancy, such as maternal smoking. The global regulation of the PCBs’ usage and waste disposal is extremely important in order to prevent the potential hazards on human health and the further contamination of the environment.

Reference: Casas M, et al. Prenatal exposure to PCB-153, p,p’-DDE and birth outcomes in 9000 mother-child pairs: Exposure-response relationship and effect modifiers. Environ Int. 2015 Jan;74:23-31.