Autism environmental causes

It is thought that the causes for autistic behavior are a combination of genetic makeup and environmental factors. Although the right genes must be present, not all children with these genes develop autism. Speculate on possible environmental causes. 

Deth R, Muratore C, Benzecry J, Power-Charnitsky VA, Waly M. 2007. How environmental and genetic factors combine to cause autism A redox/methylation hypothesis. 

What do Gulf War Syndrome, Katrina Cough, Aerospace Syndrome, and epidemic increases in the incidence of autism, Attention Deficit Hyperactivity Disorder (ADHD), birth defects, asthma, mailroom illness, spontaneous abortion, and many cancers have in common Each of these can be associated with a single causative agent, but each can also be associated with environmental exposure to chemical mixtures that do not contain any of the known causative agents. 

Our inability to defend ourselves against new chemicals and mixtures often results in epidemics of disease. For example, asthma, autism, infertility, and many cancers affect different parts of the body and seemingly have different etiologies. All, however, can be related to a combination of genetic predisposition and environmental exposure to chemicals. All are less prevalent where chemical exposures are lower, for example, in rural areas. All have known single chemical exposure causes and they can all be related to low level exposure to chemical mixtures. The toxic effects of chemical mixtures are explored in the chapters that follow. 

The failure of the apoptosis process has been reported as a possible cause of autism in some individuals [63, 64], Chemical exposure may shift the tightly regulated balance of neurotrophic signals regulating apoptosis and cause an increase or decrease in the cell numbers of a region of the nervous system. However, the effect of environmental substances on apoptosis in the developing brain has not been studied to a great extent. 

Landrigan PJ (2010) What causes autism Exploring the environmental contribution. Curr Opin Pediatr 22 219-225... 

Not quite. Autism in identical twins can be caused by a shared fetal environmental impact rather than by direct genetic transmission. The reality is that like mental retardation, autism is a behaviorally defined syndrome with a possibly wide variety of both genetic and nongenetic causes. The often-quoted concordance rate of 90 percent among identical twins is accurate for broad autism but not for severe (narrow) autism, for which twin concordance is only about 60 percent. Also in contrast to the ABC News report, the concordance among fraternal twins can be as high as 23 percent for broad autism.55... 

Exposures to developmental neurotoxins are believed to be responsible for staggering numbers of affected children. In the United States, 5-10% of public school children have learning disabilities, up to 17% of children suffer from ADHD, approximately 1% of all children are mentally retarded, and as many as 1 in 150 children bom have autism [5, 6], Though some of these effects are genetically influenced, the available evidence suggests that environmental exposures and not genetics are the primary causes for these disorders [5],... 

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