Environmental exposures are changing dramatically in location, intensity, and frequency. Around the world, shifts in industrial activity result in shifts in environmental pollutants. Coupled with the global phenomenon of climate change, and the resultant propensity for natural disasters from extreme weather, we are left with changing exposures in a changing world.
With the globalization of trade and spread of the “Western life style”, and with increasing globalization of the chemical manufacturing industry, toxic chemicals and chemical wastes have been pouring into lower- and middle-income countries (LMICs) (1). It is estimated that in 2020, the developing world will account for 33% of global chemical demand and 31% of production, compared to 1995 levels of 23% and 21%, respectively. Developing countries are also expected to lead in manufacturing of high-production-volume chemicals by 2020 (2). Because of low labor costs and less strict environmental and public health protections, manufacture and use of chemicals are increasingly moving to LMICs (3, 4).
With rapid growth and production and consumption of chemicals, coupled with insufficient infrastructure to protect public health and the environment, pollution-related chronic diseases are becoming more prevalent in LMICs (5). In LMICs, high risk of non-communicable diseases results in a “double burden”, adding this new threat to traditional problems such as infectious disease, inadequate clean drinking water, and nutrition (6, 7).
The double burden of disease
Many developing countries are undergoing an epidemiological transition in which they face the double burden of both infectious diseases and chronic diseases such as cancer, heart disease, stroke, chronic respiratory diseases, and diabetes. Once thought to be challenges for affluent countries alone, noncommunicable diseases have emerged as the leading cause of death and disability in developing countries (8). For example, 55% of new cancer cases are arising in developing nations, and could reach 60% by 2020 (9).
In addition to the increase in new cases of noncommunicable diseases, the higher prevalence of infectious diseases and other public health problems exacerbate the issue. Malnutrition and infection in early-life increase the risk of chronic noncommunicable diseases in later life (10) (see Figure 1). Infection is also one of the main risk factors for cancer. In 2008, approximately 16% of new cancer cases worldwide were attributable to infection (11).
Global climate change will further exacerbate risks to human health from toxic environmental exposures, by increasing chemicals in water, air, or sediment (12), and by adding additional stress to individuals’ immune, endocrine, and neurological systems that may increase sensitivity to pollutants (13).
Linking pollution to health effects in LMICs
Worldwide, pollution is insufficiently appreciated and inadequately quantified as a cause of disease. The health burden from both noninfectious diseases, such as cancer and cardiovascular disease, and infectious disease from factors such as parasites can be very high among exposed people. Numerous environmental substances cause adverse health effects but are avoidable. Pollution is responsible for 8.9 million deaths per year (14, 15), which is greater than the number of deaths caused by HIV/AIDS, malaria, and tuberculosis combined (16, 17). Most of these pollution related deaths (8.4 million) occur in low- and lower-middle-income countries (15).
Mothers and children are disproportionately vulnerable to the shift toward pollution-related diseases in developing countries. Children are already vulnerable because of lack of adequate nutrition and clean drinking water. Exposures to pollution can cause acute death in infancy and childhood as well as chronic noncommunicable diseases that can manifest at any point across the human life span (18).
Low-dose exposure occurring during developmental windows of susceptibility – periods in embryonic, fetal, and early postnatal life that are important to the developmental process – may have far greater effects than high-dose exposure in an adult (19). Chronic, noncommunicable diseases linked to early environmental exposures include neurobehavioral development disorders (20–23), adult and pediatric asthma (24), hypertension, obesity, diabetes, cardiovascular disease (25), and cancer (26).
Increased environmental pollution receives far less attention in global health and development assistance programs than it should. A very high standard of proof is required to establish causation between pollution and illness (27). Various components of pollution have traditionally been counted separately (see Table 1). This fragmentation, which may help facilitate identification of associations, may also minimize the total impact of pollution and thus fails to give pollution the attention it deserves in planning and policymaking. Pollutants may act together to lead to noncommunicable diseases. For example, chemicals can sometimes act together to cause cancer, even when low-level exposures to the individual chemicals might not be cancer-causing, or carcinogenic (28). Cumulative exposures over time may also lead to disease, but without a full understanding of the totality of an exposure throughout the lifespan, this association is difficult to measure.
As research informs knowledge of present conditions, our future research directions, programmatic priorities, and policy recommendations must be cognizant of pollution prevention. A regime of strong environmental health protection from pollutants is required in countries at every level of development.
Global opportunities: a model for reducing the burden of disease
Reducing the burden of disease requires focusing on the totality of environmental exposures as well as other factors, such as improving diet. Creating global networks that encourage interdisciplinary public health research will help promote research to better understand how pollution contributes to the double burden of disease and how to reduce or eliminate exposures to toxic substances.
A global initiative to promote human health sciences and technology in the Pacific Basin would enhance collaborations and communications amongst public health science investigators and promote environmental health research. The network would involve a virtual infrastructure that houses a team of scientists and engineers who do research in emerging areas of exposure biology framed on emerging global health issues. Researchers would focus on three cutting edge areas: the development of technologies to accurately predict human biological response to exposure induced by external agents; disease intervention focused on a broad, informatics-based program aimed at identification of chemical agents that result in reduction in disease burden; and the addition of modern measurement tools to modest scope epidemiological studies to provide more detailed phenotypic definition of a population. This model should allow better prediction of disease risk and should provide ways to reduce exposure to environmental contaminants.
Learning from existing models
Existing models that facilitate the transfer of information and research results can provide insight into the steps required to build an international network. Existing models also highlight the advantages of creating a coordinating program that facilitates multidisciplinary and multidirectional interactions among groups worldwide.
The NIEHS Superfund Research Program (SRP) is a model that funds university-based multidisciplinary research on human health and environmental issues related to hazardous substances. Scientists from a variety of disciplines work together on research related to remediation approaches, detection technologies, fate and transport modeling, bioavailability and ecotoxicity, and ecological and human risk assessments with the central goal of understanding and breaking the link between chemical exposure and disease. The SRP network also proactively fosters collaboration to communicate findings to relevant stakeholders.
The SRP model is working toward improving methods to share data across platforms and integrate data from a variety of scientists – from engineers to microbiologists – to enhance the knowledge base and ultimately reduce the burden of disease. By creating and integrating an environmental health knowledge architecture, the SRP will enhance collaborations and communications among environmental health science investigators, seize emerging scientific opportunities, and manage knowledge to meet public health and disease burden outcomes and products.
The WHO Collaborating Centres Network for Children’s Environmental Health is another network model. This network of research institutes around the world. Each acts as a hub to strengthen national or regional capacity to advance children’s environmental health. At the same time, collaboration and the sharing of services and expertise among centres in the network builds global children’s environmental health capacity. The network’s overall goal is to improve children’s health by preventing or reducing environmental threats by building evidence and research capacities in global children’s environmental health, coordinating and conducting collaborative children’s environmental health research, raising awareness of global children’s environmental health issues through improved education and communication strategies, and developing interventions aimed at capacity building and preventing or decreasing the burden of disease for children.
A global network would bring together scientists from multiple disciplines and countries to work toward a better understanding of the double burden of disease in LMICs. The network will also contribute to alerting the global health community of research activities, raise awareness of pollution issues, and assist in targeted messaging to improve public health.
Spitz P. Chemical industry at the millennium: maturity, restructuring and globalization. Philadelphia, PA: Chemical Heritage Foundation, 2003.Google Scholar
Trasande L, Massey RI, DiGangi J, Geiser K, Olanipekun I, et al. How Developing nations can protect children from hazardous chemical exposures while sustaining economic growth. Health Affairs 2011;30:2400–9.CrossrefWeb of ScienceGoogle Scholar
Dhara VR, Dhara R, Acquilla SD, Cullinan P. Personal exposure and long-term health effects in survivors of the union carbide disaster at bhopal. Environ Health Persp 2002;110:487–500.CrossrefGoogle Scholar
Pronczuk J BM-N, Gore F. Children’s environmental health in developing countries. In: JO N, editor. Encyclopedia of environmental health. Burlington, VT: Elsevier, 2011:601–10.Google Scholar
Suk WA, Ruchirawat KM, Balakrishnan K, Berger M, Carpenter D, et al. Environmental threats to children’s health in southeast asia and the western pacific. Environ Health Persp 2003;111:1340–7.CrossrefGoogle Scholar
Council on Foreign Relations. The Emerging Crisis: Noncommunicable Diseases. 2014. Available at: http://www.cfr.org/diseases-noncommunicable/NCDs-interactive/p33802?cid=otr-marketing_use-NCDs_interactive/#!/.
Frenk J. The Shadow Epidemic. Harvard School of Public Health Magazine. 2009. Available at: http://www.hsph.harvard.edu/news/magazine/shadow-epidemic/.
Bygbjerg IC. Double burden of noncommunicable and infectious diseases in developing countries. Science 2012;337:1499–501.Google Scholar
Noyes PD, McElwee MK, Miller HD, Clark BW, Van Tiem LA, et al. The toxicology of climate change: environmental contaminants in a warming world. Environ Int 2009;35:971–86.Web of ScienceCrossrefGoogle Scholar
Hooper MJ, Ankley GT, Cristol DA, Maryoung LA, Noyes PD, et al. 013. Interactions between chemical and climate stressors: A role for mechanistic toxicology in assessing climate change risks. Environ Toxicol Chem 2013;32:32–48.Web of ScienceCrossrefGoogle Scholar
World Health Organization. 7 million deaths annually linked to air pollution. 2012. Available at: http://www.who.int/phe/health_topics/outdoorair/databases/en/.
World Health Organization. Burden of disease from household air pollution for 2012. Geneva: World Health Organization, 2014.Google Scholar
World Health Organization. Data on the size of the hiv/aids epidemic: Number of deaths due to hiv/aids. Geneva: World Health Organization, 2014.Google Scholar
World Health Organization. Deaths: estimated deaths, data by region. Geneva: World Health Organization, 2014.Google Scholar
Bouchard MF, Chevrier J, Harley KG, Kogut K, Vedar M, et al. Prenatal exposure to organophosphate pesticides and iq in 7-year-old children. Environ Health Persp 2011;119:1189–95.Google Scholar
Engel SM, Miodovnik A, Canfield RL, Zhu C, Silva MJ, et al. Prenatal phthalate exposure is associated with childhood behavior and executive functioning. Environ Health Persp 2010;118:565–71.Web of ScienceCrossrefGoogle Scholar
Jacobson JL, Jacobson SW. Intellectual impairment in children exposed to polychlorinated biphenyls in utero. N Engl J Med 1996;335:783–9.Google Scholar
Gauderman WJ, Avol E, Gilliland F, Vora H, Thomas D, et al. The effect of air pollution on lung development from 10 to 18 years of age. N Engl J Med 2004;351:1057–67.Google Scholar
Smith AH, Marshall G, Liaw J, Yuan Y, Ferreccio C, et al. Mortality in young adults following in utero and childhood exposure to arsenic in drinking water. Environ Health Persp 2012;120:1527–31.CrossrefGoogle Scholar
Murray CJ, Ezzati M, Flaxman AD, Lim S, Lozano R, et al. Gbd 2010: a multi-investigator collaboration for global comparative descriptive epidemiology. Lancet 2012;380:2055–8.Web of ScienceGoogle Scholar
Goodson WH, Lowe L, Carpenter DO, Gilbertson M, Manaf Ali A, et al. Assessing the carcinogenic potential of low-dose exposures to chemical mixtures in the environment: the challenge ahead. Carcinogenesis 2015;36 (Suppl 1):S254–96.Web of ScienceCrossrefGoogle Scholar
About the article
Published Online: 2016-02-17
Published in Print: 2016-03-01