A semi-tangential point I wanted to make about the previous post: progress, in terms of air pollution, can be difficult to measure. Once upon a time, as I pointed out, Chicago (and lots of major American cities) had what we'd consider now to be unimaginable levels of pollution. One piece I came across suggested that Chicago housewives buy electric clothes-dryers because the particulate pollution would soil any clothes left outside to dry.

Obviously conditions have improved. But so has our understanding of air pollution. Jennifer Weuve of the Rush Institute for Healthy Aging recently co-authored a paper entitled "Exposure to Particulate Air Pollution and Cognitive Decline in Older Women":

In the study, women who were exposed to higher levels of ambient particulate matter (PM) over the long term experienced more decline in their cognitive functioning over a four-year period. Higher levels of long-term exposure to both coarse PM (PM2.5-10) and fine PM (PM2.5) were associated with significantly faster cognitive decline.

[snip]

There are few recent studies that analyze air pollution and cognitive function in older adults, but this is the first study to examine change in cognitive function over a period of time and whether exposure to the size of particulate matter is important.

That's via a New York Times roundup, "Air Pollution Linked to Heart and Brain Risks":

“Cognitively speaking, this higher exposure is as if you had aged an extra two years,” said Dr. Weuve, an assistant professor at the Rush Institute for Healthy Aging at Rush University Medical Center in Chicago. That might not sound like much, she added, but if there were a treatment “that could just delay the onset of dementia by two years, that would spare the population millions of cases of disease over the next 40 years.”

Another study, this one from the Journal of the American Medical Association, that's been making the rounds:

Short-term exposure (for up to 7 days) to all major air pollutants, with the exception of ozone, is significantly associated with an increased risk of heart attack, according to a review and meta-analysis of previous studies appearing in the February 15 issue of JAMA.

When pollution in Chicago was so bad that it blocked the sun, one concern doctors had for the youth was that children would be harmed by lack of exposure to its rays. The sun's back out, but we're learning a lot more about what we can't see.

Photograph: vxla (CC by 2.0)