Blood Chemistry
Dr. Joe Schwarcz writing at the
American Council on Science and Health delivers a breath of fresh air to those worried about "chemicals" in their blood:
Chemicals! In Our Blood!!
Perhaps you're health but are told by your doctor, after a routine blood test, that you should take statins to combat high cholesterol. Fine. But then you start wondering what else you should be testing for in your blood. After all, you've been reading about all those toxic chemicals that invade our daily lives -- nasty-sounding things ranging from pesticides and PCBs to heavy metals and flame retardants.
Ah...those flame retardants. Polybrominated diphenyl ethers (PBDEs) have been protecting fabrics, furniture, computers, and various other consumer items from fire since the 1970s, so it comes as no great surprise that their levels in the environment and in humans have been steadily rising. Toxicological studies have shown that PBDEs can impair reflexes and learning abilities in rodents and can also delay puberty in the animals by interfering with thyroid function. Shouldn't you know if PBDEs are present in your blood? So you convince your doctor to find a lab that can carry out this analysis and off goes a sample. The results come back, and you find out you have 15 nanograms/L in your blood plasma. Or 15,000 picograms per liter. Wow! This may make you hot under the collar, but you think it means you won't burst into flames.
But what realistically does this value mean? Well, it certainly means that chemists have amazing analytical capabilities. Since you have about five liters of blood in your body, you now know that you are harboring 60 nanograms of flame retardant. That is 0.000000060 grams, or roughly 1/20,000th the mass of a grain of sand. Pretty impressive technology! But what does it say about any health risk? Without further information, not much.
The presence of a chemical in the blood does not equate to the presence of risk. As everyone hopefully understands, only the dose makes the poison. We certainly would be concerned if we had data suggesting that patients with some sort of disease were more likely to have higher blood levels of PBDEs than the rest of the population, and we would then want to know at what blood levels risk becomes significant. But we do not have such data. Not for PBDEs, nor for the numerous potential toxins that can now be measured in the blood, often down to the levels of parts per trillion. What is a part per trillion? Well, it's one second in 32,000 years!
Relativly cheap lab equipment is now able to measure concentrations that 20 years ago would have been thoguht to be impossible. To the lay person, it seems that the instances of chemicals in their blood is rising but this is not the case. It is only the threshold of detection that is going down. And as Dr. Schwarcz notes in his closing (he is Canadian):
And in case you missed the news that came out the same week as "Toxic Nation," average life expectancy in Canada reached a record high in 2005. Hmmm...could it be because of all the chemicals in our blood?
Heh...
Posted by DaveH at December 16, 2005 3:54 PM