Particulate Pollutants and Autism Disorders

"When looking at health impact in a human population, not a controlled animal experiment, getting this level of consistency is, in my assessment, notable."
"For every health condition, there's a constellation of causal influences. It's not a 'one cause,  one disease' world. What this means is that for some children air pollution might be part of that causal pie of all the pieces that came together to tip the balance."
"It could actually be two or several chemicals acting together in synergy. In my world, this is considered the problem of mixtures; that a group of chemicals together could act very differently than a single chemical in isolation."
"Unfortunately, I don't think there's a lot that an individual person can do [to avoid potential pregnancy problems]. This is a classic public health problem, if you will, where it takes a village. It takes people working together to solve this problem."
Dr. Amy Kalkbrenner, environmental epidemiologist, University of Wisconsin-Milwaukee

In Dr. Kalkbrenner's world the issue is one of the impact of exposure to motor vehicle emissions in urban settings by the developing foetus having its deleterious effect when human biology comes up  against environmental degradation. Specifically the air chemistry of pollution and how in places where pregnant women are exposed to excess particle pollution the result is an increase in the number of children with autism spectrum disorder.

The issue is fine particulate matter resulting from the exhaust of motor vehicles in the burning of carbon fuel. Two types of particulate matter ensue from vehicle exhaust to mix with air; PM10, producing coarse particles less than 10 micrometers in diameter, and PM2.5, producing finer particles from auto emissions which animal studies suggest are more biologically relevant to brain developmental issues.

Aside from the matter of the two types of particles, relatively coarse and very fine, there is the chemical interaction that takes place when those particles result from within dozens of toxic air chemicals come in contact with the air, the sun, and become transformed into different compounds. It is the issue of exposure to those chemical compounds in particulate matter impacting on foetal brain development the study points to.

In the later stages of foetal development the brain undergoes a process of synaptic connectivity. Autism develops when that connectivity becomes faulty.

The discovery by scientists that weeks 31 to 36 of pregnancy appears the period when the foetus becomes most susceptible to the interfering and deleterious impacts of air pollutant particles led to the understanding of what might be happening when the natural process of development is impacted by circulating chemicals in the air that pregnant women breathe, corrupting the developing brain of the foetus they carry.

The increase of autism disorders over the past several decades has been notable. There is scientific uncertainty whether the rise is associated with greater awareness and evaluation, or whether it represents a true increase in susceptibility and occurrence due to environmental degradation. What is beyond dispute is the number of children affected; in Canada, 1 in 68 children.

That  the environment plays some role in autism development has general scientific agreement, without consensus for a single cause. Dr. Kalkbrenner places great confidence in her findings that traffic pollution is a causative, but she also qualifies that with the caution that not necessarily all instances of autism can be attributed to traffic pollution, but can arise from other causes as well.

Two U.S. states, California and North Carolina, undertook studies and Dr. Kalkbrenner looked at both that assessed pre-conception through first birthday records of over 164,000 children comparing pollution data and the number of autistic cases related to mothers exposed to higher pollution levels. Her synthesis of the studies led to her conclusion that the more traffic pollution pregnant women have exposure to the greater the chance their child will develop autism.

Her study results were published online in the online journal Epidemiology in October. Four studies have made the link between traffic pollution exposure and autism; Dr. Kalkbrenner's is the latest to be published. She has stressed the difficulty of individual women seeking a solution on their own by attempting to avoid exposure to heavy traffic pollution.

The problem is a general, global one needing to be solved by awareness and managing the risks through greater public health initiatives.