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Californian columnist Lois Henry

I'm sure a recent study looking at asthma and fine particulate matter in the San Joaquin Valley will go over like a lead balloon for some.

What it found was even as fine particulate matter (tiny bits of dust and soot also called PM2.5) dropped significantly in the years 2008-2010, asthma-related ER visits went up.

What that means, as far as asthma goes, is air pollution isn't a major contributing factor.

It's well known that air pollution doesn't cause asthma, but the mantra has long been it's likely a trigger for asthma attacks.

Well, probably not, according to this study, commissioned by the San Joaquin Valley Air Pollution Control District and scheduled to be presented at the district's June 19 board meeting.

"It shows that, relative to other causes, air pollution doesn't even register" as a trigger for asthma attacks, said Seyed Sadredin, director of the air district.

The study also broke down the constituents that make up PM2.5 to ferret out which bits do the most harm.

It found that to the minimal extent PM2.5 does affect asthma, the main culprits are wood smoke and vehicle emissions. Ammonium nitrates had zero effect. That's important for dairy farmers, but we'll come back to that.

This study is an extension of a previous study released in 2011 that looked at asthma-related ER visits and PM2.5 levels during the years 2005-2007.

That study did find a strong correlation between high PM2.5 levels and hospital visits for asthma, particularly among children.

But in this latest study, the correlation shifted dramatically away from PM2.5 levels, instead showing a strong association between asthma attacks and upper respiratory infections -- colds.

In a summary describing the study, the air district states this latest study is "a reminder of the complexity of factors and processes that shape public health outcomes in the San Joaquin Valley, particularly in respect to asthma."


No such caution was included in the previous study that did show a correlation between PM2.5 and asthma ER visits.

Back then the study's findings were "important new regional evidence for the public health consequences of air pollution" and were loudly touted by activists as justification for ever more regulation.

Which is why I'm sure the new findings will be roundly booed by activists who get a lot of political mileage on the back of childhood asthma, something that pulls at all our heartstrings.

This study pours cold water on that emotional reaction.

"The other important finding was that ammonium nitrates, which are tied to dairy emissions, don't have any impact on asthma attacks," Sadredin said.

Fifty percent to 70 percent of PM2.5 pollution in the valley is caused by ammonium nitrates, Sadredin said.

If you hate mega dairies, that's a big, fat slow moving target.

But if it turns out all that ammonium nitrate isn't actually hurting anyone, why bother with it?

Sadredin said the district will use the results of this study to lay the foundation for a more risk-based approach to cutting air pollution.

The air district has been pressing the EPA for some time to allow it to regulate for different constituents within air pollution rather than regulating based on mass.

"The Clean Air Act treats all species (constituents) the same," he said. Whether they're carcinogenic or inert, it doesn't matter.

"It's a shotgun approach."

He said in mature air districts like the valley, where we've been at emission reduction for many years and have, in fact, cut pollution by up to 80 percent, the EPA should allow a more surgical approach so regulators can concentrate on those pollutants that are most dangerous.

For instance, with ozone, which is made up of VOCs and NOxs (volatile organic compounds and nitrogen oxides), our big problem is NOx.

In order to meet the EPA's new eight-hour rule for ozone, the air district has proposed allowing us extra credit for every ton of NOx we cut, rather than forcing equal cuts to VOC, which does nothing to improve public health.

Same thing with PM2.5.

"If asthma is the public health issue and ammonium nitrates don't contribute to the problem but wood smoke does, let us target that rather than engaging in a gazillion-dollar effort to go after nitrates," Sadredin said.

I ran the air district's study by another scientist in the air biz, Robert Phalen, a professor of medicine at UC Irvine and founder and co-director of the Air Pollution Health Effects Lab at Irvine.

"It's a breath of fresh air," he said, without a hint of irony.

Regulators need to better understand the pollutants they're trying to reduce. They need to analyze the public health risks of those reductions as well, he said.

"That's a fundamental problem we have with regulators worldwide," he said. "They look at something in isolation and try to drive the risk of that one factor to zero not realizing that in doing that, they may be causing more harm to public health."

Much like microbiologists have shown that being too clean can be bad for our health, he said, pollutant free air can have adverse effects as well.

For instance, if a person's respiratory tract is never challenged, particularly at a young age, it won't develop the defense mechanisms needed to survive, he explained.

Our air is exceptionally clean today compared with the past, Phalen noted.

At some point the question needs to be asked, "How clean is clean enough?"

I'm pretty sure that's a question no bureaucrat who makes a living off dreaming up more air regulations will ever answer.

Opinions expressed in this column are those of Lois Henry. Her column runs Wednesdays and Sundays. Comment at, call her at 395-7373 or email