Reducing the impact of hazardous chemicals on public health: what is known and what can be done to reduce it?

1. How are we exposed to harmful chemicals and how can their effects be prevented?

Chemicals, whether of natural origin or produced by human activities, are part of our environment.

• Naturally occurring chemicals include, for instance, arsenic and fluoride in drinking water, suspended particulate matter and sulfur dioxide from volcanic emission or forest fires, or naturally occurring toxins;
• Manufactured chemicals include industrial and agricultural products such as pesticides, petroleum products, processed metals, and products of combustion such as toxic gases and particles from industrial emissions and burning of fuel. Some chemicals are manufactured for specific uses in the products of common life, while others are unwanted by-products, wastes, or products of combustion. 

Humans can be exposed to harmful chemicals through a number of ways, from the food we eat, the water we drink, the air we breathe and our work environments. For each pathway, there are regulatory tools to mitigate that exposure, and workers can be kept safe through the application of proper safety regulations. In many developing countries, these regulations are still missing, as are the means to enforce them. That is why reduction of exposure to harmful chemicals is one the elements included in three of the Sustainable Development Goals¹: SDG 3 "Good health and well-being", SDG 12 ("Responsible production and consumption"), and SDG 6 "clean water and sanitation".

¹ www.un.org/sustainabledevelopment/sustainable-development-goals/ 

2. What is the impact of harmful chemicals on public health?

Chemical, physical and toxicological properties of chemicals vary greatly. While many of these substances are not hazardous or persistent, some are life-threatening on contact and some may persist in the environment, accumulate in the food chain, travel large distances from where they are released, and can be harmful to human health at low concentrations.

Harmful chemicals may thus have a large impact on public health². The global burden of disease attributable to environmental exposure and inappropriate management of harmful chemical chemicals amounts to at least 4.9 million deaths/year with at least 1.2 million deaths from industrial and agricultural chemicals, and acute poisonings corresponding to 2% of the total deaths and 1.7% of the total burden of disease worldwide. For instance, heavy metals, pesticides, solvents, paints, detergents, kerosene, carbon monoxide and drugs lead to unintentional poisonings that are estimated to cause 193 000 deaths annually with the major part being from preventable exposures.

Exposure to certain toxic chemicals may be associated with cancer, reduced neurodevelopment in children, Parkinson’s disease, adverse effects on pregnancy, cataracts, chronic pulmonary disease or even suicides. Over one third of ischaemic heart disease, the leading cause of deaths and disability worldwide, and about 42% of stroke, the second largest contributor to global mortality, could be prevented by reducing or removing exposure to harmful chemicals. For instance, second-hand smoke and ambient air pollution are a contributing factor for 35% of acute lower and upper respiratory infections, including pneumonia, bronchitis, otitis and bronchiolitis, the most important cause of mortality in children. These harmful exposures are also linked to low birth weights and stillbirths. The figure below indicates the number of deaths and gives Disabilty-Adjusted Life Years (DALY’s)³ attributable or not to environmental factors.

² To better understand the difference between the notions of hazard and risk in the evaluation of the properties of a chemical see the short animation video : www.youtube.com/watch?v=PZmNZi8bon8  Subtitles available in English, French, Dutch, Spanish, Chinese and Russian, German, and a French speaking version is also available here: https://youtu.be/wRmfvFYDNr8 

³ Disability-Adjusted Life Year (DALY) for a disease or health condition are calculated as the sum of the Years of Life Lost (YLL) due to premature mortality in the population and the Years Lost due to Disability (YLD) for people living with the health condition or its consequences. One DALY can be thought of as one lost year of "healthy" life. (WHO)

3. In practice, what can be done to reduce exposure?

The World Health Organization (WHO) estimates that 71% of unintentional poisonings could be prevented through better chemical safety. In different sectors, the actions that can be taken vary, but all center on better regulating, when still appropriate, chemicals and pollution. Among which:

• By Reducing or removing exposure to chemicals such as from ambient air pollution, household air pollution (in particular from coke stove), second-hand smoke, and lead, over one third of ischemic heart disease and about 42% of stroke could be prevented;
• Smoking bans. In various European and North American countries the reduction of exposure to second-hand smoke have had a positive impact on health; 
• Further control of industrial emissions in many countries, through changing the way industries deal with dust and dusty environments and the use of protective measures by workers, all measures having had a positive effect on the health of workers;
• The materials used in construction, the way cities are thought out in terms of transportation, the way water supplies are managed, can improve the health of the general population;  
• Transition from current energy sources to more healhty ones – whether fossil fuel, coal or biomass based –, which are environmentally unsustainable, have negative health consequences. 

Social determinants also influence the exposure to and the effect of environmental risks, and need to be systematically integrated into risk monitoring and policy planning.

4. What is the financial impact for society of the exposure to harmful chemicals?

It is difficult to give a global estimate, but for each sector, specific examples can help grasp the scope of the issue:

1. In Paraná, Brazil, for each dollar spent on pesticides, approximately US$ 1.28 may be spent on health care and sick leave due to occupational poisoning;
2. In Hong Kong, the direct and indirect cost of second-hand smoke is estimated at 156 million dollars a year;
3. In the US, the cost of treatment of ischemic heart disease from second-hand smoke is estimated to be between 2 and 6 billion dollars per year. Smoking bans are very cost-effective public health measures;
4. In the European Union, the economic cost of premature deaths from ambient and household air pollution is estimated to amount to 1.5 trillion EUR in the European Union.

Overall, prevention of exposure is by essence more cost-effective than treatment of the resulting diseases.

References:
1. The Public Health Impact of Chemicals: Knowns and Unknowns International Programme on Chemical Safety (IPCS) , WHO, 2016  http://apps.who.int/iris/bitstream/handle/10665/206553/WHO_FWC_PHE_EPE_16.01_eng.pdf
2. Knowns and unknowns on burden of disease due to chemicals: a systematic review Department of 1314Public Health and Environment, World Health Organization, https://www.ncbi.nlm.nih.gov/pubmed/21255392
3. Preventing disease through healthy environments - A global assessment of the burden of disease from 1300environmental risks. WHO, 2016  http://apps.who.int/iris/bitstream/handle/10665/204585/9789241565196_eng.pdf