What do pcbs do to orcas

Although we don't know whether she was ever pregnant, it is likely that she never offloaded the PCBs she carried through nursing, hence the high level in her body at the time of death. Incidentally, Hope was accompanied by a young, healthy male when she died. Initially it was thought he was her son, but now he's thought to have been an unrelated companion.

In numerous studies on other marine animals, PCBs have been found to cause a weakened immune system, poor reproductive development and malfunction of the thyroid gland, all potentially serious conditions. Any one of them might have constributed to some of the health issues found during Hope's necropsy.

Made from carbon-based petroleum products, they degrade extremely slowly and can persist in the environment for decades or more. Biological effects of these compounds in animals including humans include cancer, endocrine system or immune system disruption, and interference with brain development in the fetus.

PCBs are a family of compounds that were widely used as insulating oils in electrical transformers and capacitors, and also as ingredients in adhesives and caulking compounds. During this time, many PCB manufacturing plants nationwide carelessly dumped PCBs into nearby marine waters, and attempts to dispose of it by burning sent it into the atmosphere, dispersing it worldwide.

There are also old PCB dumps on land, where surface water can carry the chemical into the Salish Sea, more than 30 years after it was banned. DDT is an insecticide that was very effective in eradicating the mosquitoes that spread malaria, and it was widely used to control the disease worldwide. In , biologist Rachel Carson published her book, Silent Spring , which raised public awareness about the damage DDT was causing to wildlife, the threat it posed to natural systems and the health risk to humans.

Silent Spring is also credited with starting the environmental movement in the US. DDT continues to be manufactured in some developing countries, however, where it is still used to control malaria.

Until production was halted, untreated DDT waste was discharged directly into the Los Angeles sewer system where it contaminated Pacific Coast waters.

The EPA has declared the area a Superfund site, and plans are underway to begin capping and containing the most contaminated locations in PBDEs, commonly known as flame retardant compounds, are emerging chemicals of great concern. They are chemical cousins of PCBs. Although Hope was not tested for PBDEs, we include information about this family of compounds because they have been found in other marine mammals.

For 30 years PBDEs have been applied to clothing, furniture, carpets, and electronic equipment, to keep them from burning if exposed to flame or high heat. They are now present in our bodies and in the bodies of animals, including orcas. Animal studies have linked exposure to PBDEs early in life to brain abnormalities, impaired learning and behavioral changes.

European countries have banned these chemicals and Washington is among several states that have banned two PBDE compounds, a move which some scientist believe is beginning to lower environmental levels.

First, unlike other orcas that eat seals or sea lions, southern residents feed almost exclusively on chinook salmon. But chinook have been in steep decline for years, and the killer whales each need hundreds of pounds of fish each day. Meanwhile, boat traffic noise is making echolocation difficult, just as the orcas need to look farther afield for food. And when whales are hungry and working hard, they metabolize fat, releasing PCBs and other toxic chemicals from their blubber into the bloodstream.

There the pollutants can damage the immune system, increasing disease risk. It can significantly reduce fertility or act as a neurotoxin, potentially disorienting whales, further complicating the hunt for food.

And as starving whales get significantly smaller, the percentage of PCBs in their bodies increases, amplifying the impacts. Killer whales can live as long as humans, which means some of those alive today were around during the heyday of PCB use during and after World War II. And these are slow-acting contaminants, which means adults can still see impacts from exposure as calves or while they were in utero.

While Puget Sound's resident whale numbers are plummeting, nearby transient whales, which eat seals and sea lions, are stable —even though their PCB levels are often higher. Killer whale numbers in Canada and Alaska are actually increasing.

But since PCBs can affect almost every physiological function, "sometimes numbers don't speak with clarity," Ross says. For example, in the late s, harbor seals in Europe were staging a great comeback after major declines from PCBs and pesticides in the s. But shortly after government officials declared the crisis over, more than half of the seals died after being hit with a virus. Their immune systems likely had been weakened by years of exposure, Ross says.

Deforges and Ross say banning PCBs clearly made the situation better for orcas "Without that, we probably wouldn't have killer whales today," Ross says. But both maintain that countries need to act more quickly to clean up legacy pollutants, both at home and through the Stockholm Convention.

In the meantime other threats to orcas—particularly from food scarcity, ocean noise, and the looming risks from climate change—need to be curbed quickly to pull some populations back from the brink. All rights reserved. PCBs Accumulate in Top Predator While PCBs initially declined after the world stopped manufacturing them, levels in the environment have remained relatively constant in recent years.

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Scientists speculate that the remaining females may now be too old to give birth. There is no agreed upon cause for the reproductive failure of the West Coast Community orcas, however, speculation has whirled around the idea that PCBs may have caused a lack of fertility among the females as a result of its ability to mimic estrogen. One report that sheds considerable light on the question of PCBs and orca reproduction is a Institute of Ocean Studies article , which describes a study in which scientists collected fat samples from 47 live, wild orcas off the coast of British Columbia and tested these samples for PCBs, furans and dioxins.

The samples were collected from transient orcas as well as individuals form the Southern and Northern Resident Groups note that the Northern Resident Group is distinct from the Southern Resident orcas, but there is some overlap of their territories of the coast of British Columbia. This study is among the most comprehensive investigations of PCBs in orcas.

The objective of this post was to consider whether the available scientific evidence supports the claim that PCBs may drive orcas to extinction as a result of reproductive failure. It is undeniably true that orcas carry high PCB body burdens, and that these PCBs are the result of their diet, whether that diet consists of fish or marine mammals. However, based on the Institute of Ocean Studies report, it does not appear that high PCB body burdens are contributing to reproductive failure in the populations studied.

As odd as it may seem, some of the strongest evidence for orca reproductive success from this study is the much lower PCB concentrations found in the adult females compared to those detected in the adult males. Sexually immature females and males have similar PCB concentrations. The study data indicates that the orcas continue to reproduce successfully among the transient and the resident orca populations on the North American west coast despite their high PCB body burdens.

However, the study clearly does not provide support for the contention that PCBs are causing a worldwide decline in orca population. Your email address will not be published. Skip to content. Orca Characteristics and Behavior Orcas are among the top predators in the ocean.