The Environmental Health Perspectives (EHP) journal is a great resource for anyone with a keen interest in up-to-date, peer-reviewed research and news on the interrelationships between the environment and human health. The journal is published online on a monthly basis and does not require a paid subscription for viewing. EHP is the top monthly journal in public, environmental, and occupational health and the third-ranked monthly journal in environmental sciences.

Three Studies on Organophosphates & Cognitive Development

This month’s issue of EHP featured three studies, all of which detected a negative correlation between a child’s in utero exposure to organophosphates and early cognitive development.[1–3] So significant were these three coinciding articles that it warranted mention in the journal’s editorial. In their editorial, authors Kimberley Gray and Cindy Lawler label the combined findings as “compelling new data."[4] As with other previous studies measuring the effects of exposure to organophosphates, these series of studies focused on in utero exposure—at this particular stage of development the brain is thought to be most vulnerable to the effects of toxins.

Declines in Development Associated with Organophosphates Exposure

Declines in working memory, perceptual reasoning, and IQ were the measures of intellectual development most consistently associated with prenatal organophosphates exposure. Declines in working memory are particularly worth mentioning because of its significance in learning. In the words of Wikipedia, “working memory is the ability to actively hold information in the mind that is needed to do complex tasks such as reasoning, comprehension and learning." One of the first tests developed to assess working memory was called the “reading span” test. It’s a good example of working memory assessment that requires subjects to read a number of sentences (usually between 2 and 6), recall the last word of each sentence, and repeat those words in correct sequence at the end.

Working Memory is Key

Researchers now know that any decrease or impairment in working memory is highly undesirable, as it is a key predictor of learning outcomes in literacy and numeracy. In fact, studies have confirmed that a child's working memory at 5 years old is a better predictor of academic success than IQ.[5] In addition, a recent study of 37 school-age children with significant learning disabilities showed that working memory capacity at baseline, rather than IQ, predicted learning outcomes two years later.[6]

Don’t Overlook All the Details

So for any clinician who specializes in working with children, it would be important to focus on any details regarding the environment of the child’s mother during pregnancy. Aside from food consumption, proximity to farming activities or chemical industries, a parent’s occupation is a key consideration in understanding children with developmental issues. Focusing on these aspects of a child’s environment may be particularly vital when pre and postnatal diet and nutrition are deemed to be of good quality by the clinician.

~ Wesley Hurrell

References

1. Bouchard MF, et al. Prenatal exposure to organophosphate pesticides and IQ in 7-year old children. Environ Health Pespect. 2011; 119:1189–1195.p>
2. Engel SM, Wetmur J, Chen J, Zhu C, Barr DB, Canfield RL, et al. 2011. Prenatal exposure to organophosphates, paraoxonase 1, and cognitive development in childhood. Environ Health Perspect. 2011; 119:1182–1188.p>
3. Rauh V, et al. Seven-year neurodevelopmental scores and prenatal exposure to chlorpyrifos, a common agricultural pesticide. Environ Health Perspect. 2011; 119:1196–1201.p>
4. Gray K & Lawler CP. Strength in Numbers: Three separate studies link in utero organophosphate pesticide exposure and cognitive development. Environ Health Perspect. 2011;119:a328-a329.p>
5. Alloway TP & Alloway RG. Investigating the predictive roles of working memory and IQ in academic attainment. Journal of Experimental Child Psychology. 2010; 80(2): 606–621.p>
6. Alloway TP. Working memory, but not IQ, predicts subsequent learning in children with learning difficulties. European Journal of Psychological Assessment. 2009;25(2): 92–98.