In the same week a US Court found that glyphosate was a “significant factor” in another case of cancer (with a further 11,000 cases waiting to be heard), the BMJ has published a new study that shows exposure to common pesticides in-utero and during infancy is linked to an increased risk of developing Autism Spectrum Disorder (ASD).

Autism Spectrum Disorder comprises severe developmental disorders characterised by atypical socialisation, and restricted and repetitive behaviors and interests.  It is the fastest-growing neurological condition in the world.  ASD affects as many as 1 in 27 children in developed countries, primarily males.  Although there’s a strong genetic link, unfortunately there has been little research into the environmental factors that may affect genetic expression.  There is some evidence of prenatal exposure to several types of pesticides leading to impaired neurological development, with organophosphates and organochlorines most stongly linked to the development of ASD.

Based on the existing research, the authors undertook this large population based case-controlled study based on a cohort of 2961 individuals diagnosed with ASD based on criteria described in the Diagnostic and Statistical Manual of Mental Disorders version IV-R who were born in California’s agricultural Central Valley region between 1998-2010.  Of those, 445 had intellectual disability comorbidity.  The 35,370 controls were matched by sex & birth year, then by comparable exposure periods (total participants = 38,331).

California has compulsory Pesticide Use Reporting (CA-PUR), so the authors cross-referenced the usage of 11 common pesticides per month within 2000m of the maternal residence, with confirmed ASD cases.  The pesticides analysed were glyphosate, chlorpyrifos, diazinon, acephate, malathion, permethrin, bifenthrin, methyl bromide, imidacloprid, avermectin, and myclobutanil with ‘exposure’ defined as ‘any vs none’ to each substance during specific developmental periods.

The study compared data from 3 months prior to conception (this would also cover paternal exposure as sperm take an average of 72 days to mature) right through to 12 months postpartum. It was shown that the most crucial times for neurological development were during pregnancy and in the first 12 months of like (exposure pre-conception had a weaker correlation).  Prenatal exposure to the chemicals in this study showed a 10-20% increase in the risk of the child developing ASD.  For ASD with intellectual disability, the odds were around 30% higher, with chemical exposure in the first year of life increasing the risk of ASD with comorbid intellectual disability by up to 50% for some substances. Milder forms of ASD including Asperger’s syndrome and pervasive developmental disorders were excluded from the study, so the results may not reflect the true risks of these chemicals.

The biggest risk factor for the development of ASD, particularly with intellectual disability, was exposure to glyphosate primarily from birth to 12 months old, but also during pregnancy.  Other high-risk substances include chlorpyrifos, diazinon, permethrin (all 3 are insecticides), methyl bromide (multi-use insecticide), and myclobutanil (fungicide).

Although the study does not look at how these substances increase the risk of ASD, research on the gut microbiome & neurological function suggests that gut health is the link.  Indeed, a large number of people with ASD (up to 91%) have an abnormal microbial balance. Glyphosate is patented as an antibiotic, which is designed to kill bacteria. Over 93% of those with ASD have been found to have genetic mutations affecting carbohydrate metabolism, which may also affect the microbial balance and in turn, the production of neurotransmitters.  Anthony Samsel and Stephanie Seneff have a series of research papers discussing the various ways glyphosate integrates with our physiology to affect our health.



Whilst there may be many different triggers for ASD, there is definitely more research needed into the health effects of agricultural chemicals.  This study supports the premise that we need to reduce chemical exposure during pregnancy & infancy to protect early brain development.  Choose organic food, personal care items (for you & baby), cosmetics, and household products whenever possible.  Grow your own food, get to know the producers at your local Farmer’s Market, or shop online for safer, GM-free products.  Lactic acid fermentation has been shown to speed up the degradation of some pesticide residues, so fermenting grains & vegetables is an effective way of reducing chemical exposure whilst improving the gut microbiome.  Also, look for a water filter that removes PBT’s (persistent bioaccumulative toxicants) and consider a detox for both parents at least 4 months before planned conception to minimise the toxic load on the foetus & optimize genetic health.  Many of these substances remain on our food, in our soil & in the water supplies, so the chance of exposure is high, even if you don’t live within 2km of properties where they’re used.


Pesticide Exposure Linked to Increased Risk of Autism |






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