Chemicals%20in%20the%20Blood

Chemicals%20in%20the%20Blood - Yikes-There Are Chemical In...

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“Yikes-There Are Chemical In Our Blood!” Joe Schwarcz PhD Salicylic acid is a chemical! Perhaps a surprising statement to some. Why? Because the word “chemical” isn’t preceded by a pejorative adjective such as “dangerous,” “poisonous” or “toxic.” That’s unusual these days. We’re more accustomed to seeing reports, such as the recent ones generated by Environmental Defence, a nongovernment organization, which highlight the “toxic chemicals” that enter our bodies from our polluted environment. Actually, without appropriate context, “toxic chemical” is a meaningless term. Take salicylic acid as an example. It occurs naturally in a variety of fruits and plants, and is also formed in our body when aspirin is metabolized. Indeed, it is responsible for the physiological effects of aspirin, which include reducing the risk of blood clot formation. That’s why aspirin is used to treat a heart attack, and is commonly taken in small doses to prevent one. But in an overdose, salicylic acid can kill. Before childproof packaging was introduced, aspirin poisoning was a common cause of death in children. So how do we react if a test detects salicylic acid in our blood? Panic because of the presence of a “toxic chemical,” or relief because of possible protection against heart disease? Of course, without having some sort of reference value, there can be no appropriate reaction. To decide whether to laugh or cry, we would want to know what blood levels of salicylic acid have been linked to risk, and what levels to protection from disease. The mere presence of the chemical says nothing. As Paracelsus insightfully and wisely noted some five hundred years ago, “only the dose makes the poison.” Similar arguments apply to the numerous other chemicals, both man-made and natural, that find their way into our body from the environment. Certainly, these include compounds found in paints, dyes, pesticides, cleaning agents, air fresheners, gasoline vapours, plasticizers and flame retardants. But consider also that a single apple is composed of over three hundred compounds, the natural building blocks of the fruit. These include the likes of acetone and formaldehyde, both of which in the proper context can be labeled as “toxic chemicals,” but of course the amounts found in apples are way too tiny to present a risk. Yet a blood test would reveal their presence! Consuming celery, mushrooms, roast beef or beer would taint the blood with furocoumarin, hydrazine, 2-amino-3-methylimidazo[4,5-f]quinoline and ethyl carbamate, all known natural carcinogens. And there would be arsenic as well. This carcinogen occurs naturally in meat, fish and cereals. But the fact is that our bodies do not distinguish between natural and synthetic carcinogens. What matters is whether a toxic dose has been reached. Numbers matter! Let’s take flame retardants as an example.
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This note was uploaded on 08/08/2009 for the course BIOL 202 taught by Professor Y during the Spring '09 term at McGill.

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Chemicals%20in%20the%20Blood - Yikes-There Are Chemical In...

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