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.
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 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.
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