Listening to Shanna H. Swan, the average European shopper would probably look twice at daily consumption and eating habits to detect exposure to toxic chemicals.
Over her decades-long career, the PhD researcher and doctor has specialised on endocrine disrupting chemicals (EDCs) – a group of substances often described as "gender benders" because they affect the reproductive system.
"Certain EDCs – and I’ve looked specifically at pesticides, phthalates and Bisphenol A – are significantly related to human development, more strongly when exposure is foetal," Swan told EurActiv in an interview.
The US scientist often calls EDCs "stealth chemicals" because they cannot be traced as easily as other substances related for example to smoking or pharmaceuticals where you can ask the person about their consumption.
Endocrine disruptors come in many guises and therefore have to be traced back in urine or blood samples. Some phthalates like DEHP for instance are added to plastic tubes in order to make them softer.
For consumers, the risk is that contamination will happen when food enters in contact with those plastic tubes, for example when cows are milked with automatic machines that use them.
"It is measurable in milk, yes," Swan said. "Whatever is passing through that, particularly if it’s warm, it will absorb that. So for DEHP, our dominant route of exposure is through food and there’s some in water."
But there are many other possible routes of contamination, Swan says, for example when patients undergo treatment in hospital. "You also get DEHP if you are in a medical department and hooked up to a tube."
Problem not solved
Politicians have long been aware of the potential health effects of "gender bender" chemicals. These include reproductive health problems in males, hormone-related cancers including testicular, prostate and breast cancer, as well as obesity and diabetes.
The European Union has been at the forefront of efforts to regulate those substances, for example by banning the use of Bisphenol A in baby bottles, or trying to reduce the amount of pesticides used by farmers. Most importantly, EU lawmakers adopted in 2006 the REACH regulation, which for the first time requested chemical producers to prove that their products are safe before they can be allowed on the market.
So, problem solved? "Not at all," says Sawn, "we’ve only begun to solve the problem."
Looking at phthalates for instance, Swan says their elimination has focused primarily on banning them from children’s toys. This is certainly an important step, she says, but it does not protect the most sensitive organism, which is the developing foetus.
"Eliminating these phthalates from children's toys – I think it is important, excellent, I certainly support it – but I would not do that at the expense of eliminating phthalates in products to which pregnant women are exposed. Because that is the most critical target for phthalates."
Cosmetics in the spotlight
When it comes to women's exposure, cosmetic products have focused much of Dr Swan's attention.
"If we put cosmetics on our skin, our face – men, women, children, babies – we immediately get another phthalate in our body, which is DEP," she says. "And this is very clear. If we put hair spray or put a nail polish, then we inhale that phthalate which is primarily DBP."
The direct link between cosmetics use and contamination with phthalates might not appear obvious at first. But Swan has managed to isolate exposure in a way that makes no doubt to her.
Dr Swan studied a population in the state of New York which call themselves the Old Order Mennonites. This population is an anti-technology religious group similar to the Amish, which only eats biological food and uses no cars. When Swan analysed samples of their urine and blood, she found the group had almost no phthalates present at all.
A couple of women, however, did show peaks at some point. "One was a woman who used a hairspray," she recounts. "And you could see this because we asked 'What did you do before you came here and gave your urine?' And this woman said, 'Well, I was not supposed to but I used hairspray because I was going out.' And there we see the peak for MBP in her urine."
Tiny doses can make a difference
When confronted with such evidence, chemicals industry representatives invariably point to the same argument: It is not the substance that makes the poison but the dose. The presence of phthalates in human blood therefore cannot be cause for concern as long as the dose is kept within scientifically proven safety limits.
Friedhelm Schmider, director general of the European Crop Protection Association (ECPA), said the tiny levels of pesticide residue found in food "cannot be a concern" for consumers.
"It is far too low to be toxicologically relevant," Schmider told EurActiv in a recent interview.
Swan, however, thinks exactly the opposite. "There is absolutely no doubt that tiny, tiny doses of hormones can permanently alter the development of the foetus," she said. "You cannot look at the dose alone, you must look at the dose in a particular time window," she stresses, citing the developing foetus in a woman's womb during pregnancy.
Measuring the hormone levels of male rats in the womb, Swan was able to detect tiny differences in testosterone depending on whether the males were located between two males or between two females.
"The difference is significant and measurable and very, very small. It’s about a drop in an Olympic-size swimming pool. That’s how small it is. It’s an extremely low dose, one part per trillion."
For Swan, this is sufficient proof that tiny doses can alter the development of foetuses – for better of worse. In this case, "the consequence is that the rodent that is a male between two males grows to be more aggressive, more masculine in behaviour and in his general development. He will have a stronger sperm count; he will be more fertile."
Swan insists that she only mentions this study as "proof of principle that a very small amount of hormonal substance at the right time alters development."
So when people tell her that tiny doses of phthalates cannot have an effect on human health, her response is: "Maybe so, but we are seeing effects. So whatever dose it is, it seems to be doing something."
Another argument that Swan often hears to challenge her research is that she may have been measuring only one substance when a multitude of other substances might be at play, making it difficult to pin down health effects on a single chemical.
The European Chemicals Industry Council (CEFIC) has long argued that urine or blood samples only offer "a one-off measurement" which do not provide any information on whether the levels vary over time or what the source of exposure was.
"On their own, these measurements do not provide enough information to determine risk or health effects," CEFIC said about blood sampling studies. Moreover, the substances tested often relate to chemicals or pesticides which are either already banned or controlled by rigorous legislation, it said (read our LinksDossier on human biomonitoring).
On this one, Swan actually agrees. "We are never exposed to one chemical," she says. "In fact a recent study found 200 chemicals on average in babies at birth."
Some toxicologists have challenged the kind of research conducted by Swan and other environmental scientists, saying the chemicals found were well below safety threshold and that additional evidence was needed to study the combined effect of some substances.
But to Dr Swan there is now sufficient scientific evidence for regulators to take action.
"Do we need more studies? Of course we do. But do we have enough information to act on these studies that we have? I say that we do."
And when it comes to phthalates in particular, she says those might deserve specific attention from policymakers. "I feel that endocrine disruption is a category deserving its own regulation. It’s different enough from reproductive toxicity and carcinogenicity."
Labelling of consumer products
So what can consumers do to protect themselves? For Dr Swan, there are simple precautions to take: "Do not use air fresheners, do not spray things in your house, do use clean cleaning products and so on."
But there are limits to what consumers can do, she says, because product labelling is not always detailed enough. "You can check the label on the lotion but you can’t check the label on your spaghetti sauce or on your bottle of milk and so on. So we need to give consumers the tools to make informed choices. And at this point we don’t have those tools."
She also has simple advice for consumers in their daily behaviour: "For example not to store in plastic, not to microwave in plastic."
"What I tell people if you want to do the best you can – buy local produce, buy it unprocessed, buy it organic."