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BLOG: July 2007

Exhaust smoke kills, doesn't it?

It sure does, and it's no news: fine particulates alone, produced mainly by vehicle exhaust emission, kill 20,000 Americans each year (EPA). And that is only about 1/5 of total deaths attributable to main air pollutants - nitrogen dioxide, coarse particulate matter (PM10, i.e. smaller than 10 microns), fine particulate matter (PM2.5), carbon monoxide, ozone and sulphur dioxide - combined (Stieb et al., 2002).

Levels of these pollutants are directly related to death rates from heart disease, cancer, stroke, respiratory ailments, and premature death.

However, it was much easier to establish statistical link, than to figure out how exactly air pollutants cause illnesses and premature death. A recent study at UCLA's California NanoSystems Institute, published in the online journal Genome Biology, tackled the mechanism by which fine particulates cause - or worsen - cardiovascular disease. It has found out that simultaneously exposing blood vessel cell to both, fine particulates and oxidized "bad" (LDL) cholesterol, causes disproportionately high inflammatory response.

And, as you know, extended inflammation of the inner blood vessel lining leads into hardening and narrowing of blood vessels, that is - cardiovascular disease.

The conclusion, as presented by the media, is that those with elevated bad cholesterol are more at risk from damaging effects of fine particulates pollution effect on cardiovascular health. Since such conclusion seems somewhat incomplete, let's glance over the implications.

Finding that exposing blood vessel cells to both free-radical sources, fine particulates and oxidized cholesterol, caused disproportionately large inflammatory response is something to expect. It boils down to a simple arithmetic. Every cell has certain antioxidant capacity, mainly depending on the available superoxide dismutase enzyme, but also on other antioxidants (superoxide catalaze, glutathione, vitamins C, A and E). If these neutralize, say, 2/3 of the free-radical level of either fine particulates or oxidized cholesterol alone (assuming them, for simplicity, nearly identical), the level of remaining still active free radicals is four fold - not twice - greater when both of these free-radical sources are present at once.

And the more cell-damaging free radicals remaining, the more "inflammatory genes" turned on.

That is, of course, oversimplification, but the point is that your fine-particulate-induced cardiovascular risk at a given pollution level depends not so much on your "bad" cholesterol levels, as it does on the

level of oxidized cholesterol present in your body, and thus levels of antioxidants available.

Obviously, the two are directly related. High antioxidants level can keep oxidized cholesterol at the necessary (metabolic) minimum. And if you have enough of antioxidants, they can also take care of other damaging oxidizers, such are fine particulates.

In short,

it is your nutritional status that will ultimately determine your fate, more than any other single factor.

If you are deficient in zinc, manganese and copper, your superoxide dismutase enzymes action - among others - will be compromised. And if you are also deficient in C, A and E vitamins, you'll be at a high risk from developing cardiovascular disease (and others), with or without elevated "bad" cholesterol.

A recent study (Laden et al., 2006) has found that for each decrease of 1μg/cub.m in fine particulate level (annual avg.), death rates from respiratory and cardiovascular diseases decrease by 3%. Knowing that over 1 million Americans die each year from these diseases, the recent EPA's move to discard its own 13.4μg/cub.m annual average recommendation, and settle for 15μg/cub.m in order to spare industry from additional expenses, will result in some 50,000 more deaths from these diseases annually (that, of course, assuming the study numbers are correct, and a very unlikely scenario in which the 13.4μg/cub.m standard would be actually enforced).

Fine particulates, carrying carcinogenic chemicals like benzene, butadiene, and formaldehyde, are also the main cancer-causing air pollutant. Most of the fine particulates air-pollution - and related cancer deaths (~80%) - comes from diesel engines fine particulate emission. By far the worst offenders are trucks and buses (including school buses, exposing children to unacceptably high health risk levels). At the estimated 580 fine-particulate-caused cancer deaths per million, over 70-year period, for the U.S. as a whole, it comes to some 2,500 deaths each year.

EPA's "acceptable" air pollution level, which would cause as little as 1 cancer death per million (580 times lower than the national average) sounds much like daydreaming.

Of course, all these numbers are no more than tentative estimates. But they do paint a big picture, which is not pretty. It underlines again how critically important can be to minimize your toxic exposure on one side, while maximizing your body's nutritional status and detoxifying efficiency, on the other.