Jeffrey Weld, Dept. of Biology
Iowa's biggest gamble has nothing to do with casinos or the Lottery. We're all players in a bet that chemical technology at work in our homes, offices, and farm fields, is doing us no harm. The industry-sponsored mantra "Better Living Through Chemistry" that ushered in a synthetics revolution is turning out, thanks to recent advances in biological risk assessment, to be naive and short sighted. Widely used chemicals in plastics and pesticides are affecting living things in a most subtle yet profound way--disfiguring the sex organs of animals and interfering with reproduction. What had been a safe wager is growing far riskier as the science matures, so that we face the classic addict's predicament--chemical dependency despite accumulating signs that it is damaging our health.
Synthetic compounds that make plastic bendable and pesticides sticky also behave like animal hormones--estrogen, testosterone, and others. Lately this list of "pseudohormones", pollutants that interfere with our endocrine systems, has exploded to include a broad menu of the most common materials in our environment--candy wrappers to dish soap, teething toys to nail polish. What's new is not that synthetics can mimic hormones--DDT and PCB were identified as endocrine disruptors decades ago--but at what tiny amounts these apparently benign chemicals are having potent effects. In the early 1990's, all hormone mimics appeared to be "feminizers" acting as pseudoestrogens. The short list included chemical plasticizers, pesticide surfactants, and the ever-present PCB, and they were linked to such broad effects as breast cancer in men and women, reproductive tract malformation, and sterility in male animals. But with each year comes news of other, more pervasive compounds that are both masculinizers and feminizers. They include diesel exhaust, the adhesive component in dental sealants, mosquito repellants, dishwashing detergents, and pine sterols from paper mills.
The same "andro" that St. Louis Cardinals slugger Mark McGuire admitted to using during his record-breaking 1999 home run streak has been identified as the culprit in masculinizing fish and slugs in rivers and creeks downstream from paper mills in Alabama. Both males and females have grossly exaggerated male sex organs, rendering many of the female fish sterile and uncharacteristically aggressive. The detective work of researchers at Samford University pinpointed waste pine sterols, converted to andro by creek bottom bacteria, as the cause.
Something in diesel exhaust--even with soot particles filtered out, causes masculinization of newborn rats. Researchers in Tokyo found last February that the fetuses of mother rats that breathed significant amounts of filtered diesel exhaust possessed delayed or abnormal testes and ovaries. The mother's blood had ten times the normal level of testosterone. Their study preceding this one had found young adult males sperm production to be diminished by one-third when exposed to diesel exhaust. Florida, downstream recipient of just about everyone's effluent, has a panther population decline crisis where more than half of the panthers born between 1985 and 1990 had undescended testes and unbalanced hormone levels leading to sterility.
Pesticides acting as environmental estrogens are believed to be the cause. And Florida's Alligator population, particularly at sites adjacent to pesticide manufacturing, have a ten-fold increase in hatchling mortality. Adult males in one Florida lake have ovaries instead of testes, and the females produce far too many eggs.
Hitting closer to home are the surfactants that give detergents their dirt-binding capacity, and pesticides or herbicides their cling to target weeds or bugs. This ubiquitous class of chemicals, alkylphenols, have been found to decrease the size of testes and lower sperm count in males rats. Related compounds, pthalates, used in making ubiquitous flexible polyvinyl products, caused dramatic decline in testosterone and missing or blood-filled testes in rats, according to a recent EPA study. The Center for Disease Control recently found pthalate residues occurring at an alarming rate in the urine of randomly tested children and adults.
Technology addicts rationalize these sorts of studies as bad news for rats, slugs, fish, alligators, and panthers, but we're humans. The thing is, hormone physiology is widely shared (biologically, conserved) in the animal kingdom--we all use estrogen, testosterone, and the cell receptors that bring the effects to life. And we do have indirect evidence of something afoot in the human condition, namely inexplicable increases in prostate abnormality, breast and ovarian cancers, declining sperm counts, and precocious onset of puberty--all of these events closely intertwined with blood hormone levels. Baby-boomers are the first generation ever to be exposed to these agents from cradle to grave and there's plenty of evidence that our addiction is harming wildlife if not ourselves. We need to rein in our technology habits by adopting more long-term views when making purchasing and political choices, and through cleaner, simpler ways of living.