Chemicals can have a long-term impact on health. Today most of us face quintuple exposures: at work, at home, in the air, in water and in food. But for too long governments and regulatory agencies have adopted a ‘wait and see’ philosophy.
There are currently well over 80,000 commercial chemicals available around the world, although not all are used widely or in great quantities, and more than 700 new chemicals come on the United States market each year.
Years ago, Wendy Chavkin, professor of clinical population and family health at Columbia University, coined the phrase ‘double jeopardy’ for women exposed to hazards at work and at home, but the reality is than most of us now face quintuple exposures to chemicals – at work, at home, in the air, in water and in food – far more than half a century ago. Do we know what long-term health hazards are presented to employees and the public by these chemicals, at what doses and after what length of exposure?
Recent estimates of over 26,500 deaths per year from air pollution by diesel and other traffic fumes in England and Scotland, along with thousands of deaths each year from occupational cancers, indicate we have grossly underestimated the consequences of such exposures in the past on the public and workers who may run the highest risks.
If we know what the effects are or could be, are we capable of controlling – and indeed removing – any major threats to public health from such chemicals through regulators and markets?
These are still very difficult questions to answer, even with better screening through existing regulations. They are much debated in scientific and environmental circles and the popular media. Responses range from ‘everything is under control’ to ‘chaos rules’; from what has been termed ‘chemophobia’ to ‘criminal complacency’. There have been arguments on the one hand about overregulated ‘red tape’ controls of chemicals in the workplace and on the other about an inability to identify, diagnose and record many occupational and environmental diseases caused by or related to chemical exposures.
There has been a resurgent interest in occupational, but not environmental, cancers caused by chemical exposures, and little recognition of the many other diseases they can cause. These range from chronic respiratory diseases, adverse reproductive effects to immunotoxic, neurological and cardio-vascular diseases. They are under-reported or not reported at all.
Our lack of understanding of the exact mechanisms of toxicity of many of the chemicals we use alone and in combination with other chemicals and other processes is thrown into the mix.
Decades ago, researchers attempted to tease out if there was any relationship between exposure to radiation and the presence of organo-chlorines in women who were flight crew and had breast cancer. Now we would also be asking questions about the shift patterns and chemical exposures of female and male employees in this group.
The International Agency for Research on Cancer also suggests that globally 7 to 19% of all cancers may be due to toxic environmental exposures, but relatively few of these will be recorded.
There are still huge problems with the lack of comprehensive chemical toxicity assessments. In 2006, in the USA it was estimated that even with chemicals used in high volumes, only around 10% had partial hazard assessments available and none had complete hazard assessments. In the late 1990s the USA Environmental Protection Agency (EPA) found that 43% of high-volume chemicals used had no toxicity information available at all and only 7% had a full set of basic toxicity information. Since then the data gap has not been closing but, on the contrary, new threats to public health have emerged.
Too little, too late
Two examples, an old and a new chemical hazard, illustrate the problems surrounding long-term disease recognition and how standards have been set almost always too late towards tougher and lower levels, as regulators try and catch up with the science.
For centuries, lead in various forms was extensively used in significant quantities with no regulation. It created polluted workplaces and wider environments. The acute neurological effects of lead in the workplace were gradually recognised and some regulations introduced. Then reproductive threats to pregnant women were recognised and such employees were excluded from the contaminated workplaces. Sometime later the reproductive hazards to men were also accepted.
More problems have emerged in the last 30 years with environmental and occupational ‘low level, long term’ exposure linked to blood pressure and heart disease, kidney function and low birth weights. It has been estimated that throughout the 2000s about 5,000 British workers a year have lead above 10 micrograms per decilitre in blood (µg/dl). Action levels are set at 50 µg/dl for employees and at 25 µg/dl for women of child-bearing age.
In some states in the US all elevated blood lead levels of more than 25 ug/dl adult and more than 10 ug/dl for children under 15 years of age have to be reported to the state authority within two days. Regulatory agents are told when more than 25 µg/dl are recorded. Since 1991, evidence has existed that children’s physical and mental development can be affected at blood lead levels of <10 µg/dl.
In California it is considered that “current science strongly indicates that worker blood lead levels should not exceed 5 to 10 µg/dl over a working lifetime”. Additionally, the EPA considers lead a probable human carcinogen.
Bisphenol A (BPA) has been used in polymer and polymer additives for several decades and both workers and consumers may be exposed to it through occupational and food packaging, particularly with paper products. The debate now rages about its potential adverse human health effects as an endocrine disrupting chemical (EDC), but it is contested by the plastics industry and some regulators because such chemicals have thrown a spanner in the toxicology works and regulatory thinking.
BPA’s adverse effects may be greatest at very low levels/parts per trillion. In 2013, the French, Danish and Belgian governments banned BPA use in infant feeding bottles and in France, from 2015, in all food packaging, containers and utensils. Despite prompting by the Swedish and French governments, the European Union has not yet introduced measures to identify EDCs, which is the first step to effective regulation.
In 2014 the World Health Organisation (WHO) recognised there had been a global failure “to adequately address the underlying environmental causes of the increasing trends in endocrine diseases and disorders” and pointed out that healthcare systems “lacked the mechanisms to address the contribution of environmental risk factors to these trends”. It goes further to argue that because of this, “the benefits to be gained by adopting primary preventive measures for dealing with them had largely remained unrealised”.
With the introduction of Registration, Evaluation, Authorisation & restriction of Chemicals (REACH) provisions in 2007 and the application of regulations such as Control of Substances Hazardous to Health (COSHH), some occupational health and safety practitioners consider the health threats from chemicals are well under control. The European Chemical Agency (ECHA) plays a role in assessing threats from existing chemicals but resources are limited, the task is huge and, as the EDC case shows, the EU is often hamstrung by hostile governments and vested interests and, therefore, unable to act. The WHO and the European Environment Agency support the application of the precautionary principle to chemicals where risks of long-term health damage to workers and the public have been flagged.
This is a safety first and ‘balance of probabilities’ approach espoused for good reasons by many in public health as the lead case study demonstrates. Yet scientists may value the null hypothesis approach more highly, seek proof of safety ‘beyond reasonable doubt’ and protect their rights to innovate first and count societal costs afterwards. The industry too is hostile to the principle because it may stifle innovation and smacks of too much market intervention. Regulators are often directed by government to respond to economic development and industry interest as a priority.
With these approaches and circumstances a ‘wait and see’ philosophy then emerges, but history shows that for many long-term occupationally- and environmentally-caused diseases this simply does not work.
Professor Andrew Watterson is head of the Occupational and Environmental Health Research Group at the University of Stirling.
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