June 5, 2013

expert reaction to report on chemical exposure and pregnancy

The Royal College of Obstetricians and Gynaecologists published a report recommending pregnant women should avoid various common food and household products, citing a lack of information about the effect of common chemicals on unborn children. 

Prof David Spiegelhalter, Winton Professor for the Public Understanding of Risk at the University of Cambridge, said:

“These precautionary ‘better safe than sorry’ recommendations are not necessarily cost-free.  They may feed anxiety, and detract attention from the known harms of bad diet, smoking and excessive alcohol.   And it is unclear how any benefits can ever be assessed.”

Prof Andy Smith, Royal Society of Chemistry Toxicology Group and MRC Toxicology Unit, University of Leicester, said:

“The exposure of unborn babies during pregnancy, or breast-fed babies, to possibly harmful chemicals – both synthetic and natural – is of increasing concern, although the real risks are uncertain.  Current methods for estimating risk are not yet capable of taking into account very low exposures to mixtures of many chemicals from the environment and the mother’s diet, as well as commercial products.

“Although UK guidelines for pregnant and breast-feeding women on a few chemicals are in place, helpfully, the authors have suggested a pragmatic lifestyle choice for mothers who are concerned to minimise their exposure to all such chemicals.  This concerns a number of precautions in eating, use of household and personal care products, and avoidance of over-the counter painkillers and ‘natural’ remedies, but at the same time the authors have put this in perspective of the major benefits of a good diet and refraining from smoking and drinking alcohol while pregnant.”

Prof Warren Foster, Department of Obstetrics & Gynecology at McMaster University Ontario, said:

“Acknowledgment that although epidemiological studies have linked exposure to some chemicals with a spectrum of adverse health outcomes, these studies demonstrate associations only and do not infer causality.  Moreover, the authors also correctly note that other studies have failed to demonstrate the same association.  Thus, it cannot be concluded that exposure to chemical contaminants cause the adverse health outcomes listed leading to the need for animal studies where the hypotheses raised by these epidemiological studies can be tested in carefully controlled experiments.

“Concentrations of environmental contaminants are decreasing in the environment. The authors also note that pesticides are so highly regulated that human exposure to pesticide residues is minimal.  This is an important point and it should be emphasized that the ability of analytical chemists to detect chemicals has significantly increased as a result of important advances in the equipment used to measure chemicals in the environment and body tissues.  Hence, published articles today report very low concentrations of chemicals in human tissue samples that could not have been detected a decade ago. It is therefore important to remind people that simple measurement of a chemical in tissue is not equivalent to having an adverse health outcome.  For example, every person has measureable amounts of E. coli in their bowel but rarely does this pose a problem for their health.  Similarly, copper can be measured in the circulation of everyone but it is only when the concentrations are very high that adverse health effects are encountered.

“Phthalates and Bisphenol A receive quite a bit of attention in the report consistent with the media attention received by these chemicals.  It is also noted that changing the diet can result in lower concentrations of metabolites measured in the urine.  What was not stated and is important to recognize is that, Bisphenol A has a very short half-life and studies by Justin Teegaurden have shown that, even when consuming a diet high in Bisphenol A, measureable levels of free BPA in the serum were rarely detected suggesting that efforts to modify diet and avoid exposure are unlikely to have any beneficial effect in avoiding adverse health outcomes.  Furthermore, while phthalates are indeed in many commercial products and thus exposure is wide-spread, the animal studies conducted to date show that adverse outcomes occur only with very high concentrations that are orders of magnitude above human exposure.  Consequently, although the data suggest that exposure to these chemicals are common it is highly unlikely that potential adverse health outcomes will occur.  However, altering the diet to include more fresh foods is a more healthy alternative that will reduce exposures to these chemicals if people remain concerned.”