Don’t have the time to scrutinise scientific reports to learn about harmful chemicals? No worries, we’ve got you covered. Scroll down to get some quick facts!

Hormone disruptors

We’re surrounded by man-made chemicals. They’re components of the vast majority of consumer products around us. That may not come as a shock to you. But did you know that many of them mess with our hormones? Here are three ways men, women and children are affected by hormone-disrupting chemicals.

Everyday items like electronics, scented products, plastics, clothes, and food packaging often contain endocrine-disrupting chemicals that alter your hormonal system. And they’re used for things you would probably never think of. You know that special smell of a new car..? Yep, that’s been linked to hormone disruptors.

These chemicals may have far-reaching consequences for human health and have, for example, been connected to higher risks of cancer, infertility, ADHD, and obesity. In one study, 95% of tested people had chemicals in their bodies that are known to reduce sperm count and quality. This highlights the widespread exposure and health impacts associated with these chemicals.

“Even at low levels, these chemicals may disturb foetal development”

Pregnant women, in particular, face significant concerns as many chemicals can be transferred from mother to child through the placenta and breast milk. Even at low levels, these chemicals may disturb foetal development. Exposures during this crucial period can have adverse health consequences throughout the child’s life and may even impact future generations.

Let’s have a look at three ways hormone-disrupting chemicals are affecting us negatively:

1. Western men’s sperm count has more than halved

You probably know someone who is having problems getting pregnant. One reason for this may be that in the last 40 years, the sperm count of men in the Western world has declined by 59%. Many researchers believe this is connected to exposure to hormone-disrupting chemicals through everyday products.

Coincidentally, this change in men is happening at the same time as many people in Western societies are delaying efforts to conceive a baby until the woman is in her thirties. At this point, women’s fertility is declining rapidly, which really creates a double whammy for fertility.

2. Harmful chemicals increase the risk of breast cancer

When young girls are exposed to hormone-disrupting chemicals, they’re more likely to reach puberty at an early age. But kickstarting puberty isn’t a great idea. Going through puberty early not only increases the likelihood of facing mental health challenges, it also extends the duration a woman is exposed to oestrogen throughout her life. This prolonged exposure increases the risk of developing breast cancer in the future.

Many times, exposure to harmful chemicals is not about an immediate health impact. It’s rather a chain of events that can have consequences on a woman’s health down the road. Understanding is vital to minimise long-term health impacts.

3. We’re polluted from birth

The health impacts of hormone-disrupting chemicals aren’t limited to adults — or even children. These substances also affect babies still developing in their mothers’ wombs. One study, for example, found 137 toxic chemicals in the umbilical cord. But, just like the young girls hitting puberty earlier, the effects of these toxic substances may not show immediately. It can take many years before noticing any effects.

Hormone-disrupting chemicals are normal ingredients in many everyday products, like perfume and plastics. But knowing exactly which products contain them is difficult since very few hormone disruptors are banned and there are no legal requirements to put warning labels on the products.

Plastic pollution

Overflowing landfills, beaches covered with plastic debris, floating garbage patches and animals entangled in plastic products. These are some very visual examples of what plastic pollution does to our planet. But what about the things we can’t see? Here are three invisible examples of the plastic pollution crisis that you might not know about.

We all have vivid images in our minds of overflowing landfills and litter-strewn beaches. But some of the most concerning consequences of plastic pollution are actually hidden from plain sight. From rampant plastics production reliant on fossil fuels all the way down to microscopic particles and chemical pollutants leaching into the environment, the plastic pollution crisis extends far beyond what meets the eye. 

Below, we look at three examples of these invisible threats, shedding light on some of the hidden harms of plastic pollution.

1. 99% of plastics are made from fossil fuels

It’s not just about plastic waste — the production phase is equally concerning. A whopping 99% of all new plastics are made from oil and natural gas. And the industry producing them emits about 2 billion tons of CO₂ per year (that’s around 5% of the world’s total greenhouse gas emissions).

Plastic production is, in other words, a really big driver of climate change. In fact, between the years 2000 and 2019, the production of plastics doubled. This plastic production rate places an immense strain on our planet’s climate and ecosystems as it depletes non-renewable resources and intensifies plastic pollution concerns.

“400 different harmful chemicals can be present in each of the major types of plastic”

2. Plastics often contain toxic chemicals

Plastics often contain a variety of harmful substances, which can have detrimental consequences for both the environment and human health. These chemicals leach out into surrounding ecosystems and enter the food chain, impacting wildlife and ecosystems. Human exposure to these toxins raises health risks such as hormone disruption, cancer and other serious health issues.

One study found that 26% of all chemicals used in plastics are of concern due to their hazards to people and planet. The same study also concluded that as many as 400 different harmful chemicals can be present in each of the major types of plastic materials.

3. Microplastics are ubiquitous and release harmful substances

When plastics age, they break down into microplastics and eventually nanoplastics. When this happens, harmful chemicals are released into the environment. These microplastics can now be found in every nook and cranny of the planet: from the peak of Mount Everest all the way down to the depths of the Mariana Trench.

They can also be found in the blood, lungs and placenta of humans. Studies show that an average person consumes about five grams of microplastics a week — roughly the weight of a credit card. Recent studies have linked the presence of these tiny plastic particles in our bodies to severe health issues such as heart attack, stroke and death.

PFAS

When we talk about PFAS as “forever chemicals” we really mean forever. These are chemicals that don’t degrade naturally. They keep accumulating in nature and our bodies as long as we keep producing and using them. Here are five things that make PFAS chemicals very problematic.

1. Every person on the planet has measurable levels of PFAS in their blood.

Today, every blood test carried out to detect PFAS shows the presence of these chemicals, including in young children and teenagers. For example, a large-scale EU study revealed the presence of PFAS in the blood of teenagers across nine European countries. Between 2014 and 2021, samples were collected from 2,000 teenagers aged 12 to 18 in Norway, Sweden, Slovakia, Slovenia, Greece, Spain, Germany, France, and Belgium. Among these countries, Swedish teenagers had the highest PFAS levels at 12.31 micrograms per liter, followed by French teenagers at 11.26 micrograms per liter, and Norwegian teenagers at 10.83 micrograms per liter. The European Food and Safety Authority (EFSA) recommends a maximum PFAS concentration of 6.9 micrograms per liter.

2. PFAS have been found in the most remote places of the world, from Antarctica to the Mariana Trench.

Even though chemical production occurs in urban areas, the chemicals travel far, especially via different waterways. Finding PFAS chemicals in areas such as the North Pole is normal nowadays. One study from Svalbard in Norway found 26 different types of PFAS compounds in the ice. When the ice melts, these chemicals can travel from glaciers into places like Arctic fjords and tundra. This meltwater carries a mix of pollutants, including PFAS, which messes with the whole food chain. It affects everything from tiny plankton to fish, seals, and big players like polar bears. Yes, that’s right. Us humans are not alone having PFAS in our bodies, even polar bears have even been found to have high levels of PFAS in their blood.

3. PFAS are used as an ingredient in thousands of everday products, from cosmetics to dental floss and guitar strings, to name a few.

PFAS chemicals are not a single chemical but a group of almost 10,000 man-made chemicals that share many of the same characteristics. The most infamous PFAS are probably PFOA and PFOS, which are banned. Even still, drinking water tests often find these two chemicals’ presence. Other PFAS are used in tons of everyday stuff because they’re really good at repelling water and oil and handling high temperatures. You’ll find them in things like fire extinguishing foam, non-stick pan coatings, food packaging, cosmetics, outdoor clothes, dental floss, guitar strings and more.

4. PFAS are called forever chemicals because they don’t degrade in nature.

PFAS are often referred to as “forever chemicals” since they don’t degrade over time, and can be found in the bloodstream of almost every human being on the planet. When the PFAS manufacturer DuPont started searching for clean blood samples without PFAS to compare them to the blood of their factory workers that manufactured Teflon, which is a PFAS, they found none. Apart from not degrading, PFAS are also toxic and have been linked to a number of diseases, such as cancer, liver damage and trouble getting pregnant. Studies show how manufacturers of PFAS knew about the adverse health effects of PFAS as far back as the 1970s.

5. There are over 17 000 PFAS polluted hot spots in the EU

Over 17,000 sites in Europe are considered hotspots for PFAS pollution. Because of this, some people cannot even eat the vegetables they grow in their own gardens. In addition, millions of Europeans are drinking water with higher PFAS levels than what is considered healthy, and some people have such elevated PFAS levels in their drinking water that they surpass the European Food Agency’s recommended limit for overall PFAS intake (from food, water, breathing, and skin contact) just by meeting their daily water needs.

Chemical policy

We trust that rigorous safety regulations protect us from harmful chemicals in our daily lives. But unfortunately, the reality is often far from this. Here are five shocking truths about chemicals legislation that will make you rethink everything you thought you knew about safety regulations.

When we think about chemicals in our everyday lives, we often assume there’s a robust system in place to keep us safe. But what if we told you that some of the substances that are banned in children’s toys are perfectly legal to use in food packaging? Or that the chemical industry has found a sneaky way to bypass bans on toxic chemicals by making tiny changes to their substances?

Here are five little-known truths about EU chemicals legislation that expose the system’s current loopholes.

1. Chemicals that are banned in toys are allowed in food packaging.

Another thing we put in our mouths, regardless of age, is food. This is why it’s strange that the same harmful chemicals that are banned in toys appear regularly in the packaging that covers our food. This includes food items geared towards kids, like colourful yoghurt cups.

The chemical laws for toys are stricter than for other kinds of products — which is really good. The reason for this is obviously that we want extra protection for our little ones. Kids also tend to put things in their mouths, which increases the risk of exposure to chemicals.

Unfortunately, chemicals from the packaging can contaminate the food. In general, this chemical leakage increases with heat, and smaller packaging items — such as children’s products — tend to have a higher ratio of chemicals compared to larger packaging. Moreover, many chemicals leak out at higher levels in contact with fatty and/or acidic foods.

2. By changing the molecule of a banned chemical slightly, chemical producers create new toxic chemicals that are legal to use

Molecules can be modified in several ways, and the number of potential chemicals is infinite. Chemical producers have used this fact to their advantage. When a toxic chemical is banned from use, it has been common practice to make a slight modification of that molecule to create a new, very similar, but different chemical that is not banned. However, since the changes are so small, the new chemical is often just as toxic as before.

As regulation tries to keep up with the creation of new, harmful chemicals, this process is repeated by the chemical industry. This is one reason why there are over 10,000 different PFAS chemicals.

3. Getting a permit to put a chemical on the market can take six months, but it can take 20 years to ban it

To ban a chemical from use in the EU is mostly a political process — not a scientific one. Representatives from all 27 member states must all agree, one chemical at a time, for a ban to happen. If just one country opposes the ban, it creates a stalemate. This has happened many times, particularly when there are proposals to ban chemicals used in important industries in specific countries.

So, the chemicals that have been banned so far are mostly the “easy” ones, those that everyone agrees on. Many hugely problematic chemicals have been discussed for decades in various EU committees without coming to any agreement. Meanwhile, it is perfectly legal to use them in consumer products.

To put a completely new chemical on the market, however, takes about six months.

4. The European chemical industry puts more money into lobbying and delaying regulations than any other sector

In the past 10 years, the chemical industry has spent a whopping €293 million lobbying the EU. What’s striking is that within the EU, the chemical industry spends more money lobbying and stalling chemical laws than any other sector — €33.5 million in the most recent year for which figures are available.

This shows just how much sway the chemical industry holds in influencing EU policies.

5. Chemical producers can block the chemical bans for decades by constantly asking for more scientific evidence

Some chemical producers and industries are deliberately slowing down the regulatory process to keep their chemicals on the market for as long as possible. By asking for more scientific studies of problematic chemicals and pointing out problems with existing data, it is possible to delay chemical laws for a very long time.

Within the EU’s chemical legislation, there are several expert groups that evaluate chemicals suspected of being toxic. However, in many cases, the outcome of these groups is often requests from the industry for more data to clarify concerns rather than immediate regulation. All the while, it is perfectly legal to use these harmful chemicals in consumer products.

When it’s then determined that more data is needed, industries are given several years to comply. In addition, the industry also objects to many of these requests, further extending the time a chemical can be used.

Finding the right balance in evaluating things is crucial for improving our rules and regulations. Although having more information is good, waiting for a complete picture can be unrealistic. Instead, using the precautionary principle is better, which means we can still make decisions even when we’re not 100% sure about everything.

Environmental impact

Pollution is just the tip of the iceberg. The chemical industry also drives climate change and biodiversity loss, making it one of the biggest environmental culprits on the planet. Yet, most people have no idea.

The world is facing a triple planetary crisis of three separate but interconnected global environmental crises — climate change, biodiversity loss and chemical pollution. The latter has now reached a point where scientists conclude that the amount of toxic chemicals in circulation now goes beyond what our planet can handle.

While it may seem obvious that the chemical industry is the main enabler behind the chemical pollution crisis — it might not be as well-known that the industry is also one of the main contributors to the other two. 

Climate change

The chemical industry doesn’t get much attention for its impact on climate change, but it’s a pretty big player in the carbon dioxide game. For example, did you know that the chemical industry releases six times as much carbon dioxide as flying? In fact, it’s the third-largest source of greenhouse gas emissions worldwide, emitting over two billion tonnes annually from plastics production alone. Still, this climate culprit often flies under the radar when it comes to public criticism.

Another big climate concern is the chemical industry’s extensive use of crude oil. It currently ranks as the world’s second-largest consumer of oil. This significant consumption stems from oil’s role in manufacturing virtually all types of synthetic chemicals found in consumer products. Additionally, oil serves as the primary raw material for the chemical building blocks that plastics are made from.

Biodiversity loss

Harmful chemicals are also causing problems in terms of biodiversity loss. While it’s known that exposure to toxic chemicals can lead to serious health issues in humans — like cancer and fertility problems — scientists are now discovering that wildlife is also at risk.

The long-term viability of over 50% of the world’s killer whale populations is, in fact, threatened by reproductive and immunological effects from PCB (polychlorinated bisphenol) exposure. And one of the largest threats to polar bears — after loss of sea ice habitat due to climate change — is exposure to chemical contaminants.

Moreover, bird populations have declined 20-25% since pre-agricultural times, with pesticides being one of the major causes. Pesticides are also one of the main reasons behind the decrease in the number of insect species on the planet by almost 70% since the 1970s.

Health effects

Since the 1940s, society has seen increasing rates of many diseases and health problems, including various cancers, autoimmune disorders, behavioural and attention deficit disorders, male infertility, premature puberty, and an explosion in rates of obesity and cases of diabetes.

Obviously, lifestyles have changed a great deal in the last 70 years, but so has the presence of chemicals in the environment, food and consumer goods. More than ever before, people are exposed to complex mixtures of man-made chemicals in food packaging materials, air pollution, furniture dust, electronic waste, toys and so on. Measurable levels of hundreds of man-made chemicals are routinely found in people, regardless of age or where they live.

Determining the health effects of these complex, low exposures is highly challenging to environmental health researchers: the technology to detect chemicals in people is in some cases barely a decade old, and the science for determining the effects of chemicals on health is still very much under development.

Nonetheless, as research gathers pace, evidence is mounting that everyday exposure to chemicals could be playing a significant role in the onset of health problems. Although the precise nature of these effects is not yet clear, the overall implications for health mean it is very important that exposure to potentially harmful substances is limited as much as possible.

According to the UNEP report “Global Chemicals Outlook” from September 2012 poisonings from industrial and agricultural chemicals contribute to more than a million deaths every year worldwide. This figure is among the top five leading causes of death globally, after HIV/AIDS, tuberculosis, road traffic accidents and malaria.

Carcinogens, mutagens and reprotoxins

In Europe, chemicals are classified and their use regulated according to the type of harm they can do. A particularly significant category is chemicals which are carcinogenic, mutagenic or reprotoxic (CMRs).

Carcinogens cause cancer, either by directly damaging the DNA or harming the body’s defence mechanisms against the disease. Mutagens cause changes to the DNA; since DNA damage initiates many cancers, mutagens are considered highly likely to be carcinogens. Reprotoxic substances are harmful to sexual function and development of the unborn child.

CMRs are considered to be high-risk substances. However, of the approximately 80,000 chemicals on the market, only 3,000 have undergone any substantial degree of toxicity testing, resulting in 800 being identified as CMRs. Which other chemicals should be classified as CMRs is a matter of ongoing debate and research.

Besides being a CMR, other ways for a chemical to be toxic include potential to harm the brain and nervous system (neurotoxins); ability to cause diabetes, immune and autoimmune disorders (immunotoxins), cardiovascular and respiratory disorders, obesity (obesogens) and interfere with hormone signaling (endocrine disruptors, such as those which interfere with thyroid function), ability to cause allergy (sensitizing) to name but a few.

Evidence is mounting that everyday exposure to chemicals could be playing a significant role in the onset of health problems

Windows of development

“Windows of development” concerns how the health effect of chemicals can differ depending not only on the degree of exposure but also on the timing of the exposure, with the same chemical having different effects at different times.

The body seems to be uniquely sensitive to effects when organs in the body are developing and being programmed for healthy functioning, such that if chemical exposure occurs in this period, it can cause permanent alterations in physical function, setting a person up for life-long consequences from a short period of exposure. This damage, although already caused, may not be apparent until decades later.

Endocrine disruption

Endocrine disruptors interfere with hormone signaling in the body. Because of the vital role hormones play in all physical processes in the body, including healthy development of the foetus, the growth of cancers and regulation of emotions and behaviour, EDCs are thought to play an important role in mediating many of the health problems which are becoming more common today.

Cancer

Cancer is uncontrolled, invasive cellular reproduction

Cancer is a family of around 200 diseases which begin when cells reproduce in an uncontrolled manner, invading and destroying healthy tissue. Chemicals can be carcinogenic by directly damaging DNA, increasing the risk of genetic mutations by altering cellular reproduction cycles, or by interfering with the body’s various fail-safe mechanisms which stop cancers developing.

Chemicals and cancer

The European Union CLP regulation (Classification, Labelling and Packaging of substances and mixtures) has identified 904 substances and substance groups that may cause cancer (R45 or R49), according to the European Commission ESIS database.

The International Agency for Research on Cancer (IARC) classifies 165 agents, many of which are chemicals, as either “definitely” or “probably” carcinogenic to humans, including benzene, vinyl chloride, chromium VI compounds, dioxin and formaldehyde (IARC 2010).

Endocrine disruptors and cancer

There is a growing body of evidence that endocrine disrupting chemicals (EDCs) may increase the risk of cancer by interfering with hormonal signalling in ways which make cancers more likely to initiate or grow (Diamanti-Kandarakis et al. 2009).

Exposure to EDCs during developmental periods can certainly have life-long implications for cancer risk, as was proven by the discovery that the daughters of women who took the oestrogenic drug diethylstilbestrol (DES) during pregnancy had a greatly increased risk of developing rare reproductive cancers (Herbst et al. 1971).

For chemicals we encounter in our everyday environment, studies of female mice exposed in the womb to Bisphenol A (BPA) have found they are more likely, when adults, to develop abnormal breast tissue which is more likely to become cancerous (Vandenberg et al. 2007; Murray et al. 2007).

Males can also be affected by oestrogenic compounds, with rat studies finding that BPA exposure after birth can cause an increase in pre-cancerous prostate growths in adulthood (Prins et al. 2011).

Given that prostate cancer and breast cancer are the most common cancers in men and women respectively, widespread exposure to other oestrogen-like compounds such as parabens and alkylphenols is a matter of concern.

Obesity

What is obesity?

Obesity is the excess accumulation of body fat, to the degree that it becomes harmful to health. 26 percent of men and women in the UK are obese. In the US, 32 per cent of men and 35 per cent of women are obese. By 2030, it is expected that 50 per cent of US and 40 per cent of UK adults will be obese. By this point obesity will have overtaken smoking as the biggest preventable cause of chronic, non-communicable diseases (Wang et al. 2011).

What are obesogens?

Obesogens are chemicals which affect the body’s ability to control its weight. We know that diabetes drugs cause obesity, and researchers have also discovered that the children of mothers who smoke while pregnant are much more likely to become obese (Monasta et al. 2010).

We do not really understand how chemicals can cause obesity. However, experiments have shown that the antifouling agent tributyl tin causes rats to produce more fat cells than usual (Kirchner et al. 2010). Other experiments have found that the oestrogenic drug diethylstilboestrol (DES) makes a mouse’s metabolism act as if it is in a low-food environment, so the mouse becomes fat if food is in fact plentiful (Newbold et al. 2009).

Which chemicals are obesogens?

Very few chemicals have been tested to find out if they are obesogens. Studies have found that the offspring of pregnant rats exposed to small quantities of bisphenol A (BPA) gain more weight than is normal, especially when on a diet high in fat (Wei et al. 2011). Similar effects have been found for organophosphate insecticides (Slotkin 2011).

Epidemiological studies have found that people exposed to persistent organic pollutants (POPs) tend to have more body fat than normal (Lee et al 2011). Other chemicals which may be obesogenic include non-stick PFOAs, phthalates, nonylphenol, dioxins and furans, small particulates in air pollution and some brominated flame retardants.

Diabetes

What is diabetes?

Diabetes is a group of metabolic diseases in which a person’s blood sugar levels are too high, caused by failure of the body to either produce insulin (type-1 diabetes) or respond to it (type-2 diabetes). It is becoming increasingly common, with 11 per cent of Americans over 20 years of age now estimated to have the disease.

Type-1 diabetes normally develops in childhood as the result of an autoimmune disorder where the body destroys its own insulin-producing cells. Type-2 diabetes usually develops in adults, although the age at which it develops is coming down (Koopman et al. 2005).

How are chemicals linked to diabetes?

The rise in incidence of type-2 diabetes is generally attributed to an aging population and changes in modern lifestyle such as reduced physical activity and eating more foods high in animal fats. However, researchers are beginning to find consistent correlations between increased risk of type-2 diabetes and exposure to persistent organic pollutants (POPs) such as DDT, PCBs and dioxins (Carpenter 2008, Lee et al. 2010).

Because diabetes is an autoimmune disease, can be brought on by obesity, and is a disorder of insulin resistance, then any chemicals which contribute in some way to increased risk of any of these problems may also be contributing in some way to increasing rates of diabetes. Animal studies are showing links between a range of chemicals in the environment and the development of these problems.

Which chemicals are a problem?

Contaminants associated with diabetes in humans include some air pollutants, nitrate/nitrite/N-nitroso compounds, bisphenol A, cadmium, some pesticides, some persistent organic pollutants (including dioxin and PCBs), some flame retardants, selenium and phthalates (Thayer et al 2012).

Some air pollutants, bisphenol A, some persistent organic pollutants (including PCBs) and some pesticides have been found to promote insulin resistance in animals. Air pollutants, bisphenol A, some persistent organic pollutants (including PCBs), some phthalates, some heavy metals, some pesticides and solvents have been found to increase weight gain in animals.

Since many of these chemicals, especially PCBs, flame retardants and dioxins, are produced in electronics waste streams, reducing the use of chlorinated plastics and halogenated compounds is important in electronic goods.

Thyroid function

What is the thyroid system?

Thyroid hormones perform a highly varied number of functions in many of the body’s organs and are an essential part of the body’s metabolic control system, regulating how quickly the body uses energy and governing the body’s sensitivity to other hormone signals.

One reason the possibility of chemical interference with the thyroid system is of particular interest to environmental health researchers is the key role thyroid hormones play in the development of the brain and nervous system, controlling synapse development, the growth of the myelin coating which sheathes nerve cells (essential for passing nerve signals), and proper functional arrangement of neurones in the brain.

How can disrupting the thyroid system affect health?

The mother provides all the thyroid hormone necessary for foetal development until relatively late in pregnancy. Even relatively minor fluctuations in levels of thyroid hormone in the mother’s blood during pregnancy can result in neurodevelopmental deficiencies in the foetus (Boas et al. 2006).

Children of mothers with low circulating thyroid hormone have been shown to have trouble with motor coordination, balance and other psychomotor skills. Attention deficit disorders and higher-than-average incidence of difficulties with spatial relations, perception, memory and language have been similarly linked.

Long-term low thyroid function in adults causes poor blood circulation. This reduces delivery of oxygen to body tissues and is associated with heart disease and cancer. Increased weight, depression, loss of hair and impaired cognitive function are other symptoms of low levels of thyroid hormones. There is evidence of generally reduced thyroid function in workers on primitive e-waste sites in China, thought to be due to common use of thyroid disruptors in electronic goods (Zhang et al. 2010).

Which chemicals can interfere with the thyroid system?

The thyroid system is complex and there are many ways in which chemicals can interfere with it, including inhibiting the thyroid gland’s ability to absorb iodine (phthalates and perchlorate), obstructing the enzymes which manufacture thyroid hormones (several pesticides and fungicides), and preventing thyroid hormones being activated or deactivated (lead, chromium, UV-blockers and the pesticide methoxychlor) (Patrick 2009).

Chemicals which are relatively well-researched with regard to thyroid-disrupting effects include PCBs, BPA, perchlorate, dioxins, pentachlorophenol (a breakdown product in the body of the pesticide hexachlorobenzene), triclosan and the PBDE flame retardants. Animal evidence of thyroid disruption exists for the phthalates DEHP, DnOP, DIDP, DNHP, DBP, resorcinol used in antiseptic creams and hair dyes and the flame retardant TBBPA, now the most commonly-used flame retardant in Europe (Zoeller 2010).

Neurotoxicity

What is neurotoxicity?

Neurotoxins are substances which alter the function of the nervous system by damaging brain cells or the nerves which carry signals around the body. Some researchers regard substances which cause temporary changes to the function of the nervous system as also being neurotoxic.

Disorders associated with exposure to neurotoxic substances include impaired intelligence, impaired regulation of emotional responses, behavioural problems including attention deficit and hyperactivity disorders, depression, anxiety, memory formation, impaired physical coordination and increased risk of neurodegenerative disorders such as Parkinson’s and Alzheimer’s diseases.

How can chemicals harm the nervous system?

The healthy development and long-term function of the nervous system is governed by a wide range of physiological factors. Chemicals can have neurotoxic effects by directly and indirectly interfering with these processes.

For example, in the developing foetus some chemicals may prevent brain cells forming enough contact points with each other to communicate effectively. Other chemicals can impair IQ and cause behavioural problems by altering levels of hormones which are vital for the correct development of the foetal nervous system. In this respect, endocrine disruptors which target the thyroid system are of particular concern to researchers.

As adults, chemicals and pollutants can accelerate the rate at which adult nerve and brain cells degrade and die by increasing oxidative stress in the body. This is thought to increase the risk of Parkinson’s and Alzheimer’s diseases, bipolar disorders and chronic fatigue syndrome.

Which chemicals are causing problems?

At least 200 chemicals have been identified as potentially neurotoxic in humans and over 1,000 have been shown to be neurotoxic in animals, including:

• PBDE flame retardants, associated with poorer concentration and lower scores in a range of childhood developmental and behavioural tests (Herbstman et al. 2010);
• Heavy metals such as lead and manganese, which have been shown to impair intelligence (e.g. Ciesielski et al. 2012);
• Phthalates, which impair physical coordination and reduce scores in a range of behavioural tests, with boys in particular affected (e.g. Whyatt et al. 2012);
• Exposure to air pollution, which accelerates cognitive decline in adults (Weuve et al. 2012);
• A range of pesticides, which increase risk of Parkinson’s disease and impair early mental development, affecting working memory, intelligence and perceptual reasoning (e.g. Wang et al. 2011);
• BPA, which may affect regulation of behaviour and emotion (particularly in girls) and may feminise the behaviour of male boys (Braun et al. 2011);
• Perfluorinated (non-stick and stain-resistant compounds), which may increase risk of attention disorders and impulsive behaviours (Hoffman et al. 2010)

Female reproductive health

What is female reproductive health?

In the context of chemicals and health, female reproductive health is a broad concept encompassing development of the female reproductive organs, sexual development, fertility, and the ability to give birth to healthy babies.

Issues include the age at which girls go through puberty, the age of menopause, the ease with which women can conceive, the chance of complications during pregnancy, the likelihood of giving birth prematurely or to an underweight baby, the healthy development of the foetus, and also diseases specific to the female reproductive system, such as endometriosis, polycystic ovary syndrome (PCOS) or ovarian, uterine, cervical and vaginal cancers.

How can chemicals affect female reproductive health?

Exposure to oestrogen-like chemicals is of particular interest to researchers, due to the hormone’s central role in a woman’s physiology. Clues as to the sorts of reproductive problems that might result from exposure to oestrogen-like chemicals before birth are coming from studying women who took the oestrogenic drug diethylstilbestrol (DES) while pregnant.

Between the 1940s and 1970s DES was prescribed to millions of women to prevent pregnancy complications, but was found to increase their daughters’ risk of developing breast cancer, precancerous lesions in the cervix, infertility and early menopause. Their daughters were also more likely to experience complications during pregnancy, with increased risk of preterm delivery, miscarriage, tubal pregnancy, stillbirth and preeclampsia (Swan 2000).

Subtle influences on reproductive health problems can also have broader health implications. For example, going through puberty early not only increases the risk of psychological problems, it also increases a woman’s lifetime exposure to oestrogen, which is a risk factor in breast cancer. Preterm birth and decreased birth weight increase the risk of a range of developmental and health problems for the newborn child, while early menopause increases a woman’s risk of osteoporosis, colon and ovarian cancer, heart attack and stroke.

To make things even more complicated, female reproductive health is not only determined by the function of oestrogen and other female hormones, but by many physiological processes in the body. For example, thyroid hormones play an important role in sexual maturation. The ways in which chemicals may affect reproductive health is therefore highly complex, particularly when healthy development of the foetus is considered.

How might chemicals be affecting female reproductive health?

The balance of sex hormones during development is critical so oestrogen-like chemicals are of obvious concern including phytoestrogens, some phthalates, BPA, parabens, phenols and UV filters in sunscreens, especially in light of recent research showing that a single exposure to estradiol or testosterone in newborn mice increases their risk of polycystic ovarian syndrome (PCOS) as adults (Sotomayor-Zárate et al. 2011).

Bisphenol A (BPA) is one of the chemicals most well-studied for reproductive health effects and has been found to change the development of the uterus in female primates exposed while in the womb. Possible links are also emerging between higher levels of BPA exposure and reduced numbers of viable eggs in women(Bloom et al. 2011).

The perfluorinated compounds PFOS and PFOA (also known as C8 compounds) have been linked to both delayed puberty in girls (Lopez-Espinosa et al. 2011) and premature menopause in women (Knox et al. 2011), while there is some evidence connecting phthalates, BPA and phenols with early puberty.

There is evidence that phthalates and pesticides have an effect on fertility and pregnancy outcomes, increasing the amount of time it takes a woman to conceive and increasing the risk of preterm birth and decreased birth weight (Burdorf et al. 2011).

PBDE flame retardants may also lower the chance of conception in a given time window (Harley et al. 2010), while phthalates may also increase the risk of endometriosis and uterine fibroids. Animal studies indicate that exposure to dioxin in the womb appears not only to make it more difficult for female offspring to become pregnant, but even the daughters and granddaughters of those offspring in turn (Bruner-Tran & Osteen 2011).

Male reproductive health

What is male reproductive health?

Male reproductive health refers to a man’s sexual function and fertility. It is a broad concept which includes physical formation of the genitals, sperm count, erectile function, age at puberty and risk of testicular and other male reproductive cancers.

A number of male reproductive health disorders are increasing, including malformations of the penis, low sperm count, testicular cancer (which has roughly doubled since the 1970s) and undescended testicle. The rise has been so rapid and so recent that the environment has to be a causal factor, and there is growing evidence from laboratory research that chemicals are contributing to the problem (Sharpe & Skakkebaek 2008).

How might chemicals affect male reproductive health?

Male reproductive health is complex and there are many ways in which it can be affected by chemical exposure. One area of particular concern is how chemicals can either suppress production or block the action of the hormone testosterone. If this happens while the foetus is developing, it can have a number of serious consequences for later development of the male genitalia. These include an increased the risk of the testicles not descending properly, of the penis not developing properly (a condition known as hypospadias), of low sperm count as an adult, and increased risk of testicular cancer.

Chemicals which have been shown to potentially have these effects include dioxin, organochlorine pesticides, some sun screens, some phthalates, herbicides such as linuron and diuron, vinclozolin and other fungicides such as chlorpyrifos, PBDE flame retardants and PCBs. None of these on their own have a particularly dramatic effect; however, people are generally exposed to combinations of many of these and, since the chemicals all affect the same biological system, it is possible these individual chemicals have significant combined toxicity.

A number of oestrogenic chemicals have been connected with feminizing effects in the male, including BPA, phenols, and the phthalates DINP and DCHP. PCBs, PFCs (in particular PFOS and PFOA) have been implicated in delayed puberty in boys. Dioxin, BPA and phthalate exposure is suspected of reducing sperm count in adults, while exposure to organochlorines and butyl parabens may damage the genetic material in sperm. The antimicrobial agents triclosan and triclocarban, DDT, parabens and some phthalates have been shown to affect t