Study Watch : Asthma and Epigenetics

This may seem to be to a little off topic, but please bear with me, I have a point, honest.

I ran across a study today dealing with pollution, the environment, epigenetics, and asthma. The open access study was published on Feb 16 on PLoS One and was entitled:

Relation of DNA Methylation of 5′-CpG Island of ACSL3 to Transplacental Exposure to Airborne Polycyclic Aromatic Hydrocarbons and Childhood Asthma

That's a mouthful. I think I prefer the title from a Science Daily summary of the study:

Pollution-related Asthma May Start In The Womb

I am not as familiar with the terminology and current asthma research so I am sure that I am going to be getting some of the details wrong, but here goes..

This study seems to be talking about the impact that an environmental pollutant can have on unborn children. Specifically the authors link polycyclic aromatic hydrocarbons (PAHs) to epigenetic changes in fetuses that are thought to impact some of the genetic pathways that are involved in asthma.

From Wikipedia:

The term epigenetics refers to heritable changes in phenotype (appearance) or gene expression caused by mechanisms other than changes in the underlying DNA sequence (hence the name epi - "in addition to" - genetics). These changes may remain through cell divisions for the remainder of the cell's life and may also last for multiple generations. However, there is no change in the underlying DNA sequence of the organism;[1] instead, non-genetic factors cause the organism's genes to behave (or "express themselves") differently

In crude terms you can think of epigenetics as a dimmer light switch that can turn genes on and off.

So, at the risk of oversimplifying the study it seems to be saying that an environmental factor causes epigenetic changes which can then lead to changes in gene expression which leads to asthma.

I promised a point, so here it is. If you remember I was recently talking about a study that demonstrated that identical twins could have genetic-like differences that were thought to account for the differences in the severity of their autism? My question at the time was how these differences could happen since identical twins are, well, identical.

Based on the results from this study on asthma it seems possible that it could be the environment that is causing the changes. Now why and how this could impact one twin but not the other is still a mystery to me especially considering the fact that most identical twins share resources in the womb. But as illustrated here the environmental factors that the mother is exposed to while pregnant can result in changes in her children.

Let me put this in simple terms:

Environmental pollutant + epigenetics changes might = autism

Anyone out there want to point out why I am wrong here?