Urban Environmental Quality and Human Health: Conceiving a Sustainable Future

Evidence of Disruption in the Endocrine Systems of Diverse Animals

Before the middle of the twentieth century there were a number of recurrent illnesses that killed large numbers of people. Many of these diseases were carried by insects such as mosquitoes, flies, and fleas. Malaria, yellow fever, typhus, and bubonic plagues have all been attributed to them. Furthermore, locusts, aphids and other creatures could destroy crops in a matter of days leaving the farmers destitute. Insects were viewed as threats to Man's well being that needed to be stopped. So, around the world, for thousands of years man has waged war against them.

The Romans used sulfur on the crops. Sometimes the extract of some plants helped rid the areas of the offending insects. In Mesoamerica smoking pine resin was used to keep them away. Burning tobacco leaves also helped. But none of the insecticides were as effective as the one that our twentieth century scientists invented and called dichlorodiphenyltrichloroethane (DDT). After World War II campaigns were made around the world to eradicate those insect born diseases. ⁷ DDT was amply sprayed in all coastal or wetland regions from the temperate to the tropical zones. Farmlands around the world were sprayed from the air by small airplanes thereby saving the crops to feed growing populations. For a number of years man considered himself to have won the war.

So focused on the success of the insecticide were the people that neither chemists nor biologists thought about the effects that DDT would have on insectivores or herbivores. In the late 1940s however; it was noticed that the bald eagle population was declining rapidly. Biologists observing the eagles noticed that the adults seemed to be uninterested in mating and for those who did nest the eaglets did not hatch. Abandoned eggs were studied and discovered to have very weakened shells, the babies inside had languished and died. As the studies progressed it was determined that the eagle populations in North America and Europe were declining to the point of near extinction because of DDT. Although the substance had never been intended to threaten any organism except in sects it had somehow affected the might and proud eagles.

It is hard to accept that scientists and industrialists focused solely on insecticides and their benefits without taking into account the notion of food chains. Eventually however; they did ban the use of DDT in the United States. In tropical countries where insects could breed faster and the threat of disease was still great their governments did not forbid its use. ⁸

But scientists were excitedly creating new synthetic chemicals for an array of human wants and perceived needs. Their attention was more focused on the wants of the industrialists and ultimately the economy of their respective nations. If one insecticide had proven to be noxious to some animals new, more effective compounds could be created. Attention was not concentrated however solely on insecticides. The plastic revolution had begun and the boundaries of the uses to which the products could be applied were limitless. Couched in the certainty of usefulness the industrialists overlooked effects on the ecosystems beyond the purpose for which their product was designed. And so, synthetic fertilizers and insecticides seeped into the ground and, helped with rain or irrigation water, found their way into the rivers and eventually the oceans. Petrochemical plants, plastics factories, paint companies, and oil refineries - to mention just a few industries - dispose of their wastes into the water ways near them. Those wastes too, find their way into the oceans and are considered xenobiotics. It is easy to understand that some geographic areas would be more easily contaminated than others. For example: large water features with limited exchange of water such as the Mediterranean Sea and the Great Lakes Basin are surrounded by some of the most industrialized countries or cities in the world would be the most threatened. Fossi ⁹ points out that it is precisely in this type of settings where xenobiotic levels can rise to extraordinarily high degrees threatening the lives and offspring of the organisms in them.

In 1990 dead dolphins began to wash up on the Mediterranean coasts of Spain. They appear to have died of partially collapsed lungs, breathing difficulties and abnormal movement and behavior. Spanish biologists identified the cause of death as a virus of the distemper family and thought that these were isolated cases. But, as the year progressed more dolphins died at sea and washed up in various shores around the Mediterranean: about 1,100 dead dolphins. International teams of biologists discovered that all victims showed high levels of PCB in the fatty tissues. These estrogenic chemicals which affect the reproductive functions primarily also affect the immune system as can be seen in the Mediterranean dolphin population. To Fossi and her team it was evident that the death of so many top predators in the Mediterranean Sea could be taken as a warning of potential reproductive alterations and immune malfunctions suggesting that measures should be taken to avoid reductions in population and biodiversity. ¹⁰

These observations came a bit too late to save a number of species in the Great Lakes basin where they began to experience failure to reproduce in the decade of the 1960s. Among the fatalities were the fish fed mink in ranches established around the Great Lakes where after a few years of successful breeding, the ranch populations began to dwindle as a result of mysterious reproductive problems. Normal mink females usually gave birth to four pups at a time, but the number of natants descended to two and eventually, by 1967, to zero. In the rare instances in which females did give birth the pups died along with their mother. ¹¹

Shortly thereafter on the Ontario side of the Great Lakes Basin entire potential flocks of Herring gulls were found lying on the shores in un-hatched eggs. All of the dead chicks had some grotesque deformity: missing eyes, twister bills, club feet, or adult feathers instead of down. The deformities and failure to thrive of the chicks suggested dioxin contamination in the lakes. ¹²

Gulls in California were, at the same time, behaving in very peculiar manners. Observing biologists noted unusually large numbers of eggs in various nests. As they continued their observations they noticed that pairs of females were caring for the infertile eggs as a couple while the males seemed to be totally uninterested in them or in nesting.

Another closed body of water with limited exchange of water that had endured pesticide spills was Lake Appopka in Florida. In 1980 disaster killed off 90% of the alligator population. Emergency clean up of the waters was hoped to bring back the alligators to the ecosystem's sustainable levels. However, toward the middle of the decade only 18% of alligator eggs hatched but only half the brood survived after a few days. Of the young males that did reach adulthood 60% had abnormally small penises.

Otters also became part of the devastating statistics. In the 1950s the otter populations in England's rivers and streams began to dwindle dramatically. By the mid 1980 their numbers had reduced so much that in some rivers and streams they disappeared completely. Pollutants in the form of pesticides were suspected to be the cause of their disappearance. ¹³

In July of 1998 the Journal of Wild Life Diseases reported that Norwegian scientists had been surveying polar bears near the Svalbard Islands and had discovered that seven out of the four hundred and fifty surveyed bears had both male and female genitalia. Although these were genetic females and some had even given birth to cubs they all had small penises in front of their vaginas. ¹⁴ Although the researchers admitted that hermaphroditism does occur in nature the percentage represented here was outside of the expected norms. The researchers suspected that polychlorinated biphenyls are to blame.

More recently still, is the evidence from Cardiff, Wales where starlings are showing signs of endocrine disruptions. Cardiff University researchers have a set of starlings in aviaries where their nutrition is controlled. The other group consists of free starlings living at sewage treatment plants and eating earthworms from the rocky filter beds. The worms survive on microbes that degrade the sewage. As the treatment plant starlings ingest the worms they are also consuming natural human estrogen along with DEHP, DBP, and BPA. The researchers noticed that in spring the males who consumed the estrogen mix had developed larger vocal centers, singing five times as long as uncontaminated birds and composing more complex songs. These songs appear to be very attractive to the female starlings - even the ones in captivity. However, blood tests show that the singing male starlings have compromised immune systems and are, perhaps less fit as mates. ¹⁵

Fish are not exempt from the effects of PCBs or other toxicants. Swordfish, salmon and rainbow trout are three types of fish that have demonstrated to have negative effects to chlorinated compounds. Some of them help to reduce the fish's levels of ascorbic acid which in turn reduces the hatchability of eggs, increases the number of deformed fry, and negatively affects the growth of fry, their food utilization and survival. In the males the deficiency has indicated a reduction in sperm concentration and effective motility. ¹⁶