The God Species_ How the Planet Can Survive the Age of Humans - Mark Lynas [87]
Being at the apex of the food web, human beings are especially at risk. In the late 1980s researchers in Arctic Canada discovered that Inuit women had breast-milk concentrations of PCBs up to ten times those of women farther south, thanks to the Inuit “country food” diet of seals, walrus and beluga whales, all of which accumulate toxics in their fat deposits.12 More recent surveys have confirmed that Inuit people are particularly exposed to chlordane, toxaphene, and PCBs, with mercury levels high enough to pose a risk to unborn children.13 In other parts of the world people are warned not to eat fatty or carnivorous fish because of the dangers of bioaccumulated toxics.
GOOD FOR GONADS?
Their possible effects on humans make environmental toxics one of the more successful campaigns mounted by Greens over recent decades. No one likes to be poisoned, and the fact that many of these chemicals are proven carcinogens increases public support for their elimination. Equally worrying is their sheer ubiquity: Out of 3,000 or so pharmaceutical products in everyday use, 100 have already been found in rivers and watercourses. Considerable controversy now surrounds the possible effects of phthalates and bisphenol-A (BPA), especially given that their use in baby bottles may expose newborn children to low levels of endocrine-disrupting chemicals. Both are widely used in the modern world, including in vinyl floors, cling film, cosmetics, medical products, and toys.
Even treated drinking water commonly contains traceable amounts of potentially toxic chemicals. One 2009 study of pharmaceuticals and endocrine-disrupting chemicals in U.S. drinking water looked at 19 drinking water treatment facilities serving 28 million people, testing for contamination by 51 different compounds. The researchers identified 34 of them in at least one sample of drinking water. Most common was the omnipresent herbicide atrazine, but also spotted were diazepam (Valium), naproxen, risperidone (an anti-psychotic), and fluoxetine, though none at levels deemed unsafe.14 It is a truism to say that the poison is the dose, and it is important for context to bear in mind that these contaminants may be having no effect at all at the levels identified, particularly as some of them are drugs used routinely in medicine with well-understood and minimal side effects. The levels were also much lower than commonly found residues of water disinfection like chlorine.
Indeed, there is a great deal of media mythology that has grown up around the issue of human health and fertility in regard to potentially toxic chemicals. One particularly stubborn myth—almost universally believed in my experience—is that sperm counts are falling around the world and that this threatens a worldwide crisis in male fertility. Although certainly some studies over the last 20 years have shown declining sperm counts, many more have shown no change at all. There are also great differences in sperm counts between different men according to lifestyle factors and geographical location: Counts in New York have been found to be double those in California for no obvious reason.15 Smoking is known to reduce sperm counts, as is obesity. Counts even vary in individuals, due to the recent temperature of the testicles and the time gone by since the last ejaculation.
There are also methodological obstacles that make this particular branch of medical science rather challenging. Because volunteering a sperm sample requires the subject to masturbate, it is virtually impossible for emotional and cultural reasons to get enough people from a broad enough random group to participate to make a study generally meaningful. “If collection of semen samples were as straightforward as obtaining blood samples, the nature of semen quality changes over time (if any) would have been determined decisively decades ago,” one expert complains.16 Instead, studies