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Harbour porpoise. Image: Charlie Phillips/WDC

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Toxic tides, troubled whales: the toll of chemical pollution

In last week’s blog, we examined the challenges whales and dolphins face as they travel the ocean, shedding light on the human-made hurdles they navigate. However, amongst these visible obstacles, there’s a hidden danger - chemical pollution.

Illusion of dilution

You’d think that the sheer size and vastness of the ocean would dilute any chemical pollutants. Sadly, this is not the case, especially for chemicals that persist in the environment or make their way up the food chain. Instead of dispersing harmlessly, these chemicals tend to build up to higher concentrations over time. This can lead to long-lasting effects that can cause significant harm to marine life like whales and dolphins.

Common dolphin

Can you help protect whales and dolphins from harm?

Lingering threat

Persistent organic pollutants (POPs) are a group of harmful chemicals that make their way into the sea from various sources, including factories, farms, oil spills, and improper disposal of waste. In efforts to protect human health and the environment, certain POPs have been banned or regulated by an international agreement called the Stockholm Convention.

One group of POPs you have probably heard of are polychlorinated biphenyls (PCBs). For many years, PCBs were widely used in building materials like cement, adhesives, wood floor finishes and paint, as well as heat exchange and insulating fluids in electrical equipment. But in 2004, the Stockholm Convention banned their use around the world. Despite this ban, PCBs still leak into the environment through careless disposal of existing products and governmental failure to tackle the 14 million tonnes of contaminated material around the world.

Many governments still allow industrial practices that pollute the sea with large quantities of dangerous human-made chemicals.
Many governments still allow industrial practices that pollute the sea with large quantities of dangerous human-made chemicals.

Toxic toll

Many POPs are highly soluble in fatty tissues such as blubber and tend to build up as they move through the food chain, in a process called ‘bioaccumulation’. Whales, dolphins and porpoises live long lives, are high on the marine food chain and tend to have a considerable amount of blubber. This means that when they eat contaminated fish, the POPs build up in their blubber over time. When food is scarce, or the individual is pregnant or lactating, they break down their stores of blubber to provide them with an energy supply. Breaking down blubber in this way releases a flood of toxic POPs into their body which then can be transferred to their foetus or newborn.

Toxins build-up as they move along the food chain, ending up with the highest levels at the very top.
Toxins build-up as they move along the food chain, ending up with the highest levels at the very top.

Exposure to these chemicals is extremely bad for species and populations of whales and dolphins. Impacts include problems with reproduction, like fetal deaths, difficult births, or stillbirths. The levels of PCBs in male and female whales, dolphins, and porpoises tend to rise as they grow until they reach sexual maturity. After that stage, male individuals continue to absorb PCBs from their food. However, the levels of PCBs in female whales, dolphins and porpoises decrease after they give birth to their first calf, because they pass on most of their PCBs to their newborns. It's likely that the high amount of PCBs transferred to babies in these ways can kill them. When an orca named Lulu washed up dead on the Isle of Tiree in Scotland, she had PCB levels 100 times higher than the safe limit and her body was treated as toxic waste.

PCBs can also cause cysts, cancers and disruptions in hormone function and have been linked to a weakened immune system, making whales and dolphins more susceptible to diseases and infections and reduce population growth. A decline in the number of whales has detrimental effects on the entire ocean ecosystem.

A shared responsibility

We need to address the root causes of chemical pollution in the marine environment. Industries need cleaner production practices, and agricultural activities must follow responsible and sustainable methods to minimise the release of pollutants into the ocean and rivers.

Governments and regulatory bodies must hold polluters accountable so that we can reduce the devastation chemical pollution wreaks on marine life and particularly whales and dolphins.

Research and monitoring programmes are crucial for getting a better understanding of how chemical pollution affects marine species and this knowledge must guide policymakers in implementing effective strategies to protect marine species.

Chemical toxins are passed from mothers to their calves. We must protect them.
Chemical toxins are passed from mothers to their calves. We must protect them.

Through education and outreach programmes, we intend to help people make informed choices to reduce their own contribution to pollution. By actively supporting conservation initiatives and putting pressure on governments to implement binding laws, you can become a powerful voice for change.

We want to say a big thank you to Jingle Jam for funding our new report that consolidates what is known about the harmful effects of chemical pollution on whales, dolphins and porpoises and makes recommendations for urgent and necessary changes.

You find out more and download the report here.

Please help us today with a donation

If you are able to help, every gift, whether large or small, will help us make vital changes to chemicals legislation so that whales and dolphins are protected