26 February 2014. The posts at this site generally reflect on chemical brain drain, its causes and implications. But there is very little critique. Comments submitted by readers are generally supportive. Perhaps that is predictable. But are there no critical comments? Yes, of course there are. Sometimes vested interests will comment that “there is no scientific justification for the conclusions” are some wording like that, although it is usually unclear what the critique relates to, except that the conclusions are unwelcome.
The recent Lancet Neurology article provided a chance to see how UK colleagues responded to a scientific review of the topic. So far eight colleagues have responded, and the media attention may primarily have attracted critical comments, in part reflecting media wordings, rather than the actual article. So some of the comments appear misguided, but be it as it may, here are some of the issues raised:
“I am surprised that Lancet Neurology chose to publish this paper. There is no attempt to review evidence systematically and critically. For example, trends in the prevalence of autism spectrum disorder and attention deficit hyperactivity disorder are difficult to determine because of possible changes in diagnostic practice and the completeness with which cases are ascertained. And discerning small effects of environmental neurotoxicants on outcomes such as IQ is complicated by uncertainties in the quantification of exposures and the potential for confounding by other influences on cognitive development. Because the paper lacks rigour, it is impossible to assess the validity of the authors’ claims, many of which seem highly speculative.”
“The epidemiological studies that this review looked at have reported links between toxicity of synthetic chemicals and brain development differences. However, these studies mostly identify associations rather than causal relationships. As usual thousands of chemicals of ‘natural’ source are not considered.”
“In citing new data the authors are quick to dismiss confounding factors without saying why they are able so to do. There is a willingness to extrapolate from high level exposures where toxicity is evident to the very low level exposures to some of the “new” toxicants that we now see identified by the authors.
“Some of these compounds have real benefits, for example some are fire retardants, and the often criticised phthalates are necessary to ensure the correct physical properties of disposable catheters etc.” “It is appropriate to control exposure to chemicals at all ages but the demonstrable benefits of the use of many compounds must be taken into account as well as the possibility of harm.”
P.S. There were some supportive comments, too.