Urban Environmental Quality and Human Health: Conceiving a Sustainable Future

Endocrine disrupting chemicals

According to a report on plastics made by the American Chemical Council nearly 100 billion pounds of plastics are produced in the United States each year. The plastic products are found in everything: the packaging of food and beverages, furniture, toys, medical devices, building products, electrical wiring, and vehicles. Two ingredients found in plastics: Diethylhexylphthalate (DEHP) and bisphenols A (BPA) deserve mention in this paper because of increasing evidence that their tendency to mimic hormonal activity disrupts normal endocrine systems in many different species of animals.

Bisphenol A (BPA)

To the great majority of the population one plastic is very much like other plastics. We are aware that some are softer and more flexible than others. But in general, we are ignorant of their compositions. By way of explanation for us then I will say that those plastics used in food and beverage packaging such as drinking water containers, baby bottles and the interior coating of cans are called polycarbonate plastics and epoxy resins. They contain the molecular building block bisphenol A. These products are not recycled so they usually end up in landfills as solid waste where their chemical compounds leach into the underground water. Bisphenol A, one of the most harmful compounds to the reproductive health of animals is frequently found in surface water, sewage effluents, sludge, and treated wastewater discharge. ¹⁸ One of the most fascinating aspects of these compounds is that the amount necessary to cause lifetime damage to the endocrine system is very low - parts per trillion. This is well below the concentrations suggested by the EPA in 1988.

At that time the EPA also considered that the safe upper limit of 50 micrograms per kilogram of body weight was acceptable and has maintained that standard. However, since then there have been a great number of experiments on laboratory animals and in human cells, the results of which prove differently. A recent statement by Consumer Reports.org says that studies suggest that adverse health effects can be reached from exposures of only 0.025 micrograms per kilogram of body weight. ¹⁹ Another recent report mentions the potential human health effects caused by endocrine disrupting chemicals to be: Breast and reproductive organ tissues cancers, fibrocystic disease of the breast, polycystic ovarian syndrome, endometriosis, uterine fibroids and pelvic inflammatory diseases and declining sex ratio. For males it is poor semen quality, testicular cancer, malformed reproductive tissue, prostate disease and other recognized abnormalities of male reproductive tissues. Other potential effects are impaired behavior and mental health, immune and thyroid function in developing children: osteoporosis, and precocious puberty. ²⁰

Few human studies have explored possible associations between BPA exposures and adverse health effects. While it is illegal to do laboratory studies of the effects of any kind of substance on human beings they are done on animals. It does not seem possible that a biologist or zoologist should not make a correlation between disrupted endocrine systems of vertebrates around the world and similar disruptions in humans. Nor has it taken long for scientists working independently of chemical corporate and governmental laboratories to make the connection. These scientists' interests are more in tune with avoiding further disruptions and return and a return to healthier lifestyles. The latter are more interested in the continued elaboration and distribution of their products while claiming that there is not incontrovertible scientific evidence linking BPA to any hormonal malfunction. ²¹ While the FDA and the EPA consider it important to regulate commercial chemical industry our children are being the subjects of experimentation; only not in laboratories.

Diethylhexylphthalate (DEHP)

Plastics that are flexible and stress resistant contain phthalates. These plasticizers are used to produce diverse products, including medical devices and products, flexible tubing, food and beverage packaging materials, electrical conduits, building products, construction materials, wood finishers, lubricants, perfumes, hairsprays, cosmetics, and adhesives. Of the six phthalates in common use I will focus on DEHP because of the strength of evidence demonstrating its testosterone-blocking potential in males.

DEHP is not very soluble in water and has a low vapor pressure. However, rising temperatures in the PVC container will lead to out gassing of the compound and absorbed into the food or water thus raising the risk possibilities to nearby organisms. In addition, DEHP has the ability to leach into a liquid that comes in contact with the plastic and it is known to migrate faster into oils and fats in foods; especially those packed in PVC. In soils, on the other hand, it moves very slowly because of its low solubility in water. So leaching from plastics in landfills is generally low.

The youngest of our species are most susceptible to the effects of phthalates. These, especially DEHP are the compounds used to provide the soft flexibility of many toys and mouthing devices such as teethers, pacifiers and bottle nipples. Rattles, balls, rings, and sundry toys that can be squeezed are also products that can be harmful. ²²

Medical devices such as flexible tubing contain DEHP; therefore, any solution such as blood serum, glucose drips, or salt solutions being administered to patients through this tubing is also transferring the compound. The American Academy of Pediatrics has advocated against the use of medical devices that can leach DEHP into patients and, instead to resort to DEHP alternatives. In July 2002 the FDA issued a Public Health Notification on DEHP that recommended considering alternatives to their use when high risk procedures need to be performed on male neonates, pregnant women who are carrying male fetuses, and peri-pubertal males. They continue to say that although they have not been notified of adverse effects in humans the large range of adverse effects of DEHP in laboratory animals would indicate a need for caution. The notification stresses that of greatest concern to the FDA is the types of effects on the development of the male reproductive system, and production of normal sperm in young animals.

And well they should be concerned. Not just about development of males but about all individuals. There are far too many observable connections between the abnormalities observed in different animals to continue doubting that any exposure to DEHP can cause the same problems in humans. If low doses of DEHP can be held accountable for male reproductive malformations, sperm damage, asthma and other respiratory diseases, female reproductive tract disease, premature delivery, and thyroid effects in animals both in laboratory and in the wild; it is time to take a stance against the producers of synthetic chemicals.