The chemicals that linger for decades in your blood

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Environmental journalist Anna Turns experienced a wake-up call when she had her blood tested for toxic synthetic chemicals – and discovered that some contaminants persist for decades.

In March 2022, scientists confirmed they had found microplastics in human blood for the first time. These tiny fragments were in 80% of the 22 people tested – who were ordinary, anonymous members of the public. The sample size was small and as yet there has been no explicit confirmation that their presence causes any direct harm to human health, but with more research, time will tell.

Microplastics are the subject of a lot of scrutiny. Wherever we look for them we find them. And yet, there are perhaps other less tangible pollutants that should be hitting the headlines, and which have been in our blood for decades.

Chemical pollution has officially crossed "a planetary boundary", threatening the Earth's systems just as climate change and habitat loss are known to do. A recent study by scientists from Sweden, the UK, Canada, Denmark and Switzerland highlights the urgent need to turn off the tap at source. Many toxic chemicals, known as persistent organic pollutants, or POPs, don't easily degrade. They can linger in the environment and inside us – mostly in our blood and fatty tissues – for many years.

I was curious about whether any of these chemicals were in my own blood while researching for my book, Go Toxic Free: Easy and Sustainable Ways to Reduce Chemical Pollution, I contacted a professor of environmental chemistry in Norway called Bert van Bavel. His research has focused on POPs that persist in bodies for more than 20, 30, sometimes 50 years and he analyses how high exposure in populations correlates to cancers, heart disease and conditions such as diabetes.

Bert van Bavel developed a blood test protocol for Safe Planet, a global awareness campaign established by the UN Environmental Programme that could be used to monitor the levels of these toxic chemicals in the global population.

Safe Planet highlights the harm caused by the production, use and disposal of hazardous chemicals such as flame retardants and pesticides, many of which have been banned. He designed a test to measure 'body burden' – that's the amount of these persistent synthetic chemical pollutants that accumulate in the body. Since 2010, this test has been carried out on more than 100,000 people around the world, across Europe, North and South America, Africa and Southern Asia.

Now, it was my turn. I booked an appointment at my local GP surgery and had my blood taken. I carefully packaged up the test tubes and couriered them to a specialist lab in Norway which spent six weeks analysing my blood for 100 or so POPs in line with this body burden test protocol.

Much attention has been paid to microplastics in human blood, but there are other chemicals that many of us carry that last for decades (Credit: Getty Images)

Much attention has been paid to microplastics in human blood, but there are other chemicals that many of us carry that last for decades (Credit: Getty Images)

When the results finally arrived via email, I felt quite apprehensive. The eight-page-long document detailed concentrations of so many chemicals, each with tricky-to-pronounce names. I needed help to decipher what this all meant and to work out if I should be worried about any, or if, perhaps, these levels were low enough to be insignificant.

So I called van Bavel who explained that most of the chemicals on the list were to be expected as part of the "toxic cocktail" we all have in our bodies.

Many, but not all, of these POPs are regulated by the UN's Stockholm Convention, a global treaty that bans or restricts the use of toxic synthetic chemicals such as certain pesticides, flame retardants and PCBs or polychlorinated biphenyls that were used as cooling fluids in machinery and in electrical goods in the UK until 1981.

"In your blood sample, we looked at the old traditional POPs which have been regulated and off the market so they haven't been used for many years," he explained. My results showed traces of DDE, a metabolite of the pesticide DDT that was used until the 1970s as well as low levels of PCBs. "It's a little bit frightening that if you get these chemicals in society, it's very difficult to get rid of them." Despite bans, these chemicals still persist, as many don't degrade easily.

Despite being banned a year before I was born, I still have oxychlordane in my blood which I will have passed on to my children

He was surprised to find relatively high levels of a chemical known as oxychlordane which is normally found at lower levels than DDT and more often in the US and Asia than in the UK. The pesticide chlordane was banned in the UK in 1981, just a year after I was born. Once in the body, it's metabolised into oxychlordane which was found in my blood at only 5% of the levels present in the population during the 1980s. But the 'half life' of this chemical – that's the time it takes for it to halve in concentration in my blood – is about 30 years. So not only was it probably passed to me via the womb, but I will have inadvertently passed this toxic legacy on to my own two children.

The impacts of some of the most hazardous chemicals last generations and chlordane is still used in some developing countries to this day. Chlordane is toxic by design – intended to kill insects, it also harms earthworms, fish and birds. In humans, it can disrupt liver function, brain development and the immune system plus it is a possible human carcinogen. Van Bavel wasn't alarmed by the current concentrations of oxychlordane still in my blood but he did emphasise the importance of banning toxic chemicals before they become globally prevalent and then accumulate in the human population.

But the chemicals that concerned van Bavel the most were actually from a newer class, known as PFAS or polyfluoroalkyl substances. Thousands of different PFAS chemicals are used in everyday products to repel dirt and water – waterproof clothing, stain-resistant textiles, non-stick cookware all tend to be made with PFAS, otherwise known as "forever chemicals" because they are so persistent.

Should I be worried?

"Your levels [of PFAS] are not that high but they are a reasonable concern. We found ones called PFOS (perfluorooctanesulfonic acid), PFNA (perfluorononanoate), and lower levels of PFOA (perfluorooctanoate) the one we normally find in blood samples. The test found the major ones at 'a reasonable level', not a worrying level, but the regulation is lagging behind," commented van Bavel. He described my body burden as fairly average.

"We're all exposed to these types of chemicals. They accumulate in our body but they shouldn't be there. Your levels are acceptable from a human health perspective but if we didn't have any measures in place, levels would rise and our population would see different toxicological effects. Of course, these chemicals need to be regulated and… the number of replacements is rising so we need proper measures in place [to govern them]."

Anna's Toxic Cocktail

Chlordane (insecticide) – banned in the UK, US and the EU

DDT (insecticide) – banned globally

PCBs (flame retardants, paints, cooling fluids) – banned globally

PFOS (fire-fighting foams, non-stick coatings and stain repellents) – restricted but not banned

PFNA (same as PFOS) – not yet banned

PFOA (same as PFOS) – banned in 2019

This "regrettable substitution" or replacement of one banned chemical with another similar one is a worry, especially with new emerging chemical pollutants such as PFAS, as van Bavel explains: "We don't have time to wait for research on every single chemical so we need to take a precautionary approach."

In terms of my own body burden, there's not much I can do to reduce the levels of toxic chemicals in my blood, according to van Bavel. "The sad thing is that it's very difficult for us to do something about it – we should all be very eager to regulate these compounds because they're everywhere. It's very difficult as an [individual] to avoid these background levels that we see that definitely should not be in your body. That's why we should support legislation and UN conventions that remove these compounds."

Prevention is better than cure

Better legislation is something Anna Lennquist, a senior toxicologist at the environmental NGO ChemSec, campaigns for. Based in Sweden, ChemSec aims to reduce the use of hazardous chemicals by influencing policy makers and encouraging companies to phase these chemicals out and opt for safer alternatives.

"We can reduce exposure but not eliminate it," agrees Lennquist. According to ChemSec, a huge 62% of the total volume of chemicals used in the EU are hazardous to human health and the environment. "[That's] why regulations are so critical and should protect us. Normal people shouldn't need to be bothered by these things – but we're not there yet.

"We can't be completely free from this, we have it with us from when we are born and it's so widespread in the environment – all of us have hundreds of [synthetic] chemicals in our blood these days," says Lennquist.

Toxic chemicals affect everything from our brain development to our hormone systems. Some can be carcinogenic. "Chemicals are working in many different ways in your body… some chemicals have delayed effects, for example ones that interact with our hormone systems. If you are exposed in the womb or during puberty, the effects can turn up many years later, even decades later, perhaps as breast cancers or different metabolic disorders."

So the outcomes depend not only on the type and level of exposure, but also whether that person is exposed during key stages of development. Lennquist explains that because we're never just exposed to one chemical at a time, this 'toxic cocktail' effect can be complex. Some chemicals might enhance the effect of others, some can work against each other.

"These low levels of this chemical mixture that affect hormone signalling and genetic effects are much more diffuse and difficult to link exactly – so that's why we need to do large-scale studies of populations over a long time to try to figure out what's the cause and what's the reason," says Lennquist, who remains optimistic.

Firefighters are exposed to higher than average levels of PFAS as it is still used in flame retardants (Credit: Getty Images)

Firefighters are exposed to higher than average levels of PFAS as it is still used in flame retardants (Credit: Getty Images)

New EU restrictions to ban around 12,000 substances have been proposed in what the European Environmental Bureau has called the world's "largest ever ban on toxic chemicals", but changes in regulation can be incredibly slow moving. "There is a long way to go but with the new EU chemical strategy and European Green Deal, we are hopeful that things can improve a lot. But even then, that would take a long time before that change is visible in your blood, I'm afraid."

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That's where we come in, as consumers, and more importantly, as citizens. "We can all use our voice by demanding greater transparency, clearer labelling and stricter regulation," adds Lennquist. "With pressure from consumers and everyone else within the supply chain, the chemical manufacturing industry could shift much more rapidly. And reducing toxic chemical pollution is not only good for business, but for every one of us and future generations."

Blood matters

As a regular blood donor myself, I wondered whether the NHS Blood Donation service tests for POPs like the ones in my body. As expected, they confirmed they screen for diseases such as hepatitis, not synthetic chemicals. Of course, chemical contaminants may well be the last thing on your mind if in need of a blood transfusion, but it got me thinking. Do we need to be more cautious about sharing blood and passing on legacy contaminants? Or is blood donation one way to offload toxics – because the contaminated blood flows out, and the body then produces fresh, uncontaminated blood?

Since publishing my book, new research has been published about just this. Firefighting foams are known to contain high levels of PFASs, so firefighters are exposed to higher than average levels of those chemicals. The landmark trial tested 285 Australian firefighters for PFAS in their blood over the course of one year. Some donated blood, some did not. PFAS chemicals bind to serum proteins in the blood, and researchers found that PFAS levels in the bloodstream of those donating were significantly reduced. One possible explanation is that the donors' bodies did indeed offload the PFAS-contaminated blood, and replaced it with unpolluted blood.

While it is still early days for this research, the feasibility of blood donation as a longterm, scalable solution is still questionable, as Lennquist explains: "For specifically exposed persons, like firefighters, it may be an option to empty the contaminated blood and let your body produce new blood. That requires that you will not be exposed again. For the average person the exposure is quite constant and I do not see that it could be a solution for the general population. But it definitely points to the urgency to do something about PFAS."

While removal may well be a crucial step in some cases, surely the most appropriate solution is to turn off the tap at source and prevent PFAS and other toxic chemicals entering our bodies in the first place.

Listen to My Toxic Cocktail, Anna Turns's investigation for BBC Radio 4's Costing the Earth series on BBC Sound.

Go Toxic Free: Easy and Sustainable Ways to Reduce Chemical Pollution by Anna Turns is out now.