Rats, PCBs and autism

I’ve already looked at part of Holford’s May e-newsletter (on Alzheimer’s) – now to deal with his claims re. autism:

PCBs may Contribute to Autism
Traces of a chemical banned 30 years ago caused brain abnormalities in newborn lab animals which are similar to defects in children with autism, according to a new study by University of California scientists. The new research shows brain development is skewed when animals are exposed to amounts of PCBs in the same range as some highly exposed people. PCBs were one of the world’s most widely used chemicals, their use peaking in the 1970s, mostly as insulating fluids in large electrical equipment. Although banned in the west in the 1970’s, they are still among the most pervasive contaminants on the planet, and exposure is difficult to avoid because they have spread globally and built up in food chains. Our comment: Avoidance of these
chemicals may be difficult, but supporting the bodies’ own detoxification process is likely to improve their elimination from the body. This means plenty of water, and fresh fruit and vegetables, and avoiding other substances that overload the detoxification processes.

There are a number of problems with this response to the UC study – Patrick Holford goes way, way beyond the study‘s conclusions, and his suggested ‘treatments’ for the alleged PCBs/autism link are unproven. The study itself has also been criticised.

The article is – to give it some credit – pretty explicit about its limitations. This is a study on rats – effects may or may not be replicated in humans. The article is clear that that, while it is possible that there may be a link between autism spectrum disorders and the exposure of babies and children to PCBs, “to date no evidence exists to support such a scenario”. The study’s authors do support further investigation of this scenario – but explicitly state that they do not have evidence that PCBs are linked to autism. This lack of evidence is not reflected in Holford’s summary of the article.

Holford also advises detoxifying from PCBs through “plenty of water, and fresh fruit and vegetables”. I haven’t been able to find any evidence of efficacy for this approach. One of the nasty things about PCBs is the way that they accumulate in your body if you are exposed to them; sadly, if someone has been exposed to high levels of PCBs then doctors can only offer symptomatic treatment. In terms of dietary interventions, all I could find was a warning that “PCBs stored in fat can be mobilized by the patients crash dieting” (i.e. if you fear that you’ve suffered too much PCB exposure, seek medical advice and don’t rush into any radical dietary changes).

The final thing to note is that there are broader issues around the quality of the article which Holford is referencing. Autism Diva covers this better than I could – questioning some of the claims of an ‘autism epidemic’, and asking why populations exposed to high levels of PCBs don’t show a correspondingly high level of autism.