Sunday, June 9, 2013

Claim: California air pollution causes birth defects

Wow!  That's terrible!  These guys were actually able to show CA's pollution is killing children!
Or....did they?  If you read one, studies of this kind tend not to be helpful is finding causality.  If anything, all they do is muck up the waters, or maybe a better metaphor would be that they don't clear the haze, they create more smoke:

We aimed to investigate whether ambient air pollutant and traffic exposures in early gestation contribute to the risk of selected congenital anomalies in the San Joaquin Valley of California, 1997–2006. Seven exposures and 5 outcomes were included for a total of 35 investigated associations. We observed increased odds of neural tube defects when comparing the highest with the lowest quartile of exposure for several pollutants after adjusting for maternal race/ethnicity, education, and multivitamin use.
Well first of all, seven exposures and 5 outcomes appear to me to be quite meaningless.  But I guess statisticians roll that way.

junkscience.com brings up a problem with studies such as this.  They call it the multiple comparison fallacy.   The links they provide are a little high-brow for me, so I did a little research to find something in more layman's terms:

The name "multiple comparisons fallacy" appears to come from the science of epidemiology, where comparisons may be made between a diseased group and a healthy group in order to find a difference between the two that might point to the cause of an epidemic. For instance, if every member of the diseased group drank from a particular well and no member of the healthy group did so, that would suggest that the pathogen might be present in the well water. In order to find the source of an epidemic, multiple comparisons between the groups may be drawn.

The author goes on to give a really good example of this: A study done to show correlation between high voltage lines and leukemia. The study showed a very strong correlation between the two.  But the author goes on:
In inductive reasoning, there is always some chance that the conclusion will be false even if the evidence is true. In other words, the connection between the premisses and conclusion is never 100%―that's only for deductive reasoning. So, the question arises: what level of probability―called a "confidence level"―are we willing to accept in our reasoning? In scientific contexts, the confidence level is usually set at 95%.

The author makes this comparion thst I think points to the real problem with the CA study:
The multiple comparisons fallacy is occasionally referred to as "the Texas sharpshooter's fallacy", but I use this name for a different type of mistake. The anecdote that gives rise to the name is that a Texan shoots randomly at the side of a barn, then draws a bullseye around a cluster of bullet holes and claims to be a sharpshooter. This story fits the mistake of jumping to the conclusion that a random cluster of data must be causally related better than it does the multiple comparisons fallacy. A better anecdote for the latter would be a shooter who first draws the bullseye, then randomly shoots twenty times at the barn. Having made one bullseye, the shooter then proceeds to conceal the nineteen misses and claims to be a sharpshooter.  

So...was it chance?  Or was it REAL? One thing we do know, with reference to the electrical line/cancer relationship:
During the last 20 years, multiple studies have been published reviewing the effect of high-power voltage lines on human health. Among the most recent was a study from England of more than 83,000 workers in the electricity industry. Researchers found no increase in brain cancer or overall death rate when compared with those who did not work around electromagnetic fields. A study in 2012 from Italy compared exposure to high voltage lines among children with birth defects and normal children. They found no increased exposure among the kids with birth defects. Reports from major research centers in at least nine countries have come to similar conclusions:

    There is no compelling evidence of any health hazard from power lines.

    If power lines have any effect on human health, it is small.

    Research should continue to look for even a small effect on health.

These results are reassuring, although they cannot completely declare power lines risk-free. In fact, in another study (published in June 2005), children living within 600 meters of a power line had higher rates of leukemia than those living farther away. However, based on limitations of this type of research (including the fact that electromagnetic fields were not actually measured in the homes of these children), the authors of this study were not convinced that power lines truly caused a higher than expected rate of childhood leukemia.
I did some more research into more of these studies.  Here are a few:

Urban Air Pollution Linked to Birth Defects for First Time; UCLA Research Links Two Pollutants to Increased Risk of Heart Defects

Exposure to two common air pollutants may increase the chance that a pregnant woman will give birth to a child with certain heart defects, according to a UCLA study that provides the first compelling evidence that air pollution may play a role in causing some birth defects.

Pregnant Los Angeles-area women living in regions with higher levels of ozone and carbon monoxide pollution were as much as three times as likely to give birth to children who suffered from serious heart defects, according to a study published in the Jan. 1 edition of the American Journal of Epidemiology.
And another:

Ambient Air Pollution and Risk of Birth Defects in Southern California
Similarly, risks for aortic artery and valve defects, pulmonary artery and valve anomalies, and conotruncal defects increased with second-month ozone exposure. The study was inconclusive for other air pollutants.

Air Pollutants and Our Health
Air pollution can harm lung development in children, can help cause early childhood asthma, and can produce a range of respiratory symptoms in children and adults. Higher air pollution levels have also been associated with a higher incidence of heart problems, including heart attacks, and toxic air pollutants can cause non-cancer health effects, and can increase the risk of developing cancer.
Aortic valve defects, pulmonary artery and valve anomalies, lung development harmed, asthma in children, cancer, neural tube defects such as anencephaly, encephalocele, and spina bifida and the list just seems to go and on and on!!

So, in essence, there isn't anything pollution doesn't cause.  In my book, if something is shown to cause everything...in reality...it causes...nothing.

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