IQ, pesticides, special ed: LATimes article misses fundamental points of human study designs.

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http://www.environmentalhealthnews.org/ehs/blog/los-angeles-times-misses-feature\

s-of-pesticide-study-design

Article misses fundamental points of human study designs.

The Los Angeles Times misinterprets four key aspects of studies that

find a mother's pesticide exposures during pregnancy can affect the

child's intelligence.

/Posted by Joe Braun and Volk/

A recent Los Angeles Times article

<http://articles.latimes.com/2011/apr/21/news/la-heb-pesticide-children-20110421\

>by

Marissa Cavallos described three new studies reporting that pesticide

exposure during pregnancy may be associated with lower IQ in children.

The three studies -- conducted in New York City and Salinas, Calif. --

measured pesticides in pregnant women and followed their children for up

to nine years. They found that children born to pregnant women with

higher pesticide concentrations had lower IQ scores.

Cavallos misses four important features of these studies: 1) effects of

small IQ shifts, 2) pesticide exposure measures 3) sources of pesticide

exposure and 4) consistency across studies.

First, she underestimates the effects of small IQ shifts. She states

that the pesticides are " slightly " harmful and that the 1 to 7 point

drop in IQ found in the studies was " small. " For an individual, these

changes may not be substantial. However, these are not trivial changes

in a population where small shifts in the mean IQ can have substantial

effects on the number of children who need special education.

Imagine two populations of one million children each. One population has

a mean IQ of 100. At the high and low ends of the distribution -- called

the tails -- about 23,000 people at the high end would be called gifted

(IQ greater than 130) and 23,000 people at the low end would be

intellectually disabled (IQ less than 70). In the other population the

mean IQ is 98 -- now 16,000 would be gifted and 31,000 would be

intellectually disabled. Even if pesticide exposure is only associated

with a two-point drop in IQ, that population would have thousands fewer

gifted and highly productive children and thousands more intellectually

disabled children who require additional resources for education. These

" slight " decreases in IQ can have profound effects on the education and

livelihoods of children.

Second...

More

<http://www.environmentalhealthnews.org/ehs/blog/los-angeles-times-misses-featur\

es-of-pesticide-study-design>

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Maternal residence near agricultural pesticide applications and autism

spectrum disorders among children in the California Central Valley.

<http://www.ncbi.nlm.nih.gov/pubmed/17938740>

EM, English PB, Grether JK, Windham GC, Somberg L, Wolff C.

Environ Health Perspect. 2007 Oct;115(10):1482-9.

Paraoxonase gene variants are associated with autism in North America,

but not in Italy: possible regional specificity in gene-environment

interactions. <http://www.ncbi.nlm.nih.gov/pubmed/16027737>

D'Amelio M, Ricci I, Sacco R, Liu X, D'Agruma L, Muscarella LA,

Guarnieri V, Militerni R, Bravaccio C, Elia M, Schneider C, Melmed R,

Trillo S, Pascucci T, Puglisi-Allegra S, Reichelt KL, Macciardi F,

Holden JJ, Persico AM.

Mol Psychiatry. 2005 Nov;10(11):1006-16.

Organophosphates (OPs) are routinely used as pesticides in agriculture

and as insecticides within the household. Our prior work on Reelin and

APOE delineated a gene-environment interactive model of autism

pathogenesis, whereby genetically vulnerable individuals prenatally

exposed to OPs during critical periods in neurodevelopment could undergo

altered neuronal migration, resulting in an autistic syndrome. Since

household use of OPs is far greater in the USA than in Italy, this model

was predicted to hold validity in North America, but not in Europe.

Here, we indirectly test this hypothesis by assessing

linkage/association between autism and variants of the paraoxonase gene

(PON1) encoding paraoxonase, the enzyme responsible for OP

detoxification. Three functional single nucleotide polymorphisms, PON1

C-108T, L55M, and Q192R, were assessed in 177 Italian and 107

Caucasian-American complete trios with primary autistic probands. As

predicted, Caucasian-American and not Italian families display a

significant association between autism and PON1 variants less active in

vitro on the OP diazinon (R192), according to case-control contrasts

(Q192R: chi2=6.33, 1 df, P<0.025), transmission/disequilibrium tests

(Q192R: TDT chi2=5.26, 1 df, P<0.025), family-based association tests

(Q192R and L55M: FBAT Z=2.291 and 2.435 respectively, P<0.025), and

haplotype-based association tests (L55/R192: HBAT Z=2.430, P<0.025).

These results are consistent with our model and provide further support

for the hypothesis that concurrent genetic vulnerability and

environmental OP exposure may possibly contribute to autism pathogenesis

in a sizable subgroup of North American individuals.