Environmental Health in Latin American Countries
Summary and Keywords
The relationship between environment and health is part of the history of medicine and has always been important to any study of human health and to public-health interventions. In Latin America many health improvements are related to environmental interventions, such as the provision of better water and sanitation services. Latin America’s development, industrialization, and sweeping urbanization have brought many improvements to the well-being of its populations; they have also inaugurated new societies, with new patterns of consumption. The region’s basic environmental-health interventions have needed to be updated and upgraded to include disciplines such as toxicology, environmental epidemiology, environmental engineering, and many others. Multidisciplinary and inter-sector approaches are paramount to understanding new profiles of health and well-being, and to promoting effective public-health interventions.
The new social, economic, labor, and consumption aspects of modern Latin American society have become more and more relevant to understanding the complex interactions in the region’s social, biological, and physical environment, which are essential to explaining some of the emerging and re-emerging public-health problems. Environmental health, as concept and as intervention, is simple and easily understood, but no longer sufficient to achieve the levels of health and well-being expected and required by these new realities. Many global changes such as climate change, biodiversity loss, and mass migrations has been identified as main cause of ill health and are at the center of the sustainable development challenges in general, and many are critical and specific public health. To face this development, other frameworks have emerged, such as planetary health and environmental and social determinants of health. Public health remains central to some, such as the improved environmental-health agenda, while others assign public health a relative position in a variety of overarching frameworks.
Keywords: environmental health, health and environment, climate change, biodiversity, toxicology, air pollution, basic sanitation, WASH, sustainable development, SDGs, Agenda 2030, Planetary Health, environmental determinants of health
The U.S. National Environmental Health Association (NEHA) defines Environmental Health as the:
science and practice of preventing human injury and illness and promoting well-being by identifying and evaluating environmental sources and hazardous agents, and limiting exposures to hazardous physical, chemical, and biological agents in air, water, soil, food, and other environmental media or settings that may adversely affect human health.
(National Environmental Health Association, 2013)
In Latin America this definition focusing on the physical environment needs to consider where people live, work, and play, which is determined by local and general social, economic, and political conditions. Accordingly, the definition as stated in general terms is essentially valid for the region, but practice and new knowledge production need to contemplate the effects of the surrounding realities, as well as knowledge and frameworks from other fields, such as the “social determinants of health.”
Maurice Strong and Ignacy Sachs, architects of the UN global environment conferences in Stockholm (1972) and Rio (1992), used the concept of “eco-development,” which says that economic growth, reduction of inequalities, and protection of environments are essential to conducting “Spaceship Earth” toward economic, social, and environmental development, and to assuring decent work for all (Bresser-Pereira, 2013). This concept makes provision for the region’s specificities and was the basis for the modern definition of “sustainable development.” As a result, in the region, both the concept and the practice of environmental health are closely related to the basic principles and framework of sustainable development.
Latin America’s abundant natural resources and vast biodiversity play important roles in health-disease processes, particularly those involving live pathogens. The U.S. Geological Survey (Bright et al., 2013) represented the interactions among environmental drivers, environment, and organisms in a diagram (fig. 1). This diagram summarizes the dynamics of the processes occurring in the environment that ultimately cause disease, and is very well suited to addressing the particularities of Americas region.
As framed in figure 1, Environmental Health Science can be defined as the study of the interrelations among the quality of the physical environment, the health of the living environment, and human health (fig. 2). It focuses on the environment–health interface, where these three spheres intersect.
Environmental Health is thus a complex, comprehensive theme of global dimensions, with effects at the local level. These characteristics make it of special interest for Global Public Health and its interactions with other thematic areas, including sustainable development and its economic, environmental, social, and peace and security dimensions (UN System Task Team, 2012). The distinctive features of these dimensions in the Americas region have been well described and are recognized both for specific, local-level impacts and for their global relevance to environmental phenomena such as climate change. One example of this global relevance to climate change is the Amazon’s positive potential contribution to fixing carbon; at a more local level, climate change impacts the region in terms of the vulnerability of the Caribbean and desertic areas in South America.
This regional susceptibility to global environmental changes is aggravated by unplanned urbanization, intensive natural-resource extraction, major impacts from agribusiness, extensive use of agrochemicals, and biodiversity loss caused by changes in the occupation of territories driven by intense migration to expanding production frontiers.
Of all global changes, climate change has very particular, unprecedented effects on the region. It is affecting the water cycle and, consequently, vector behavior (mosquitoes), and is exacerbating the effects of extreme weather events, with special significance for the Caribbean islands and coastal areas of continental countries. This is so important to the region that in 2011 its ministries of health approved a strategy and a plan of action on climate change (Pan American Health Organization, 2011b). Climate change also bears on the rapid, unplanned urbanization seen in most of the region’s cities, the effect of which has been that most of the population lives in chaotic conditions. This is a major environmental-health challenge in Latin America, with such significant impacts on public health that the region’s health ministries approved a resolution in 2011 setting up a regional strategy and plan of action on urban health, designed to deal with the health effects of disorganized urbanization (Pan American Health Organization, 2011a).
The UN Agenda 2030 and Sustainable Development Goals (SDGs) (UN General Assembly, 2015) are ultimately an expression of the contemporary holistic view of the world. Among the issues they address is the complexity of environmental health and global health, both of which are embedded in the SDGs and their implementation targets and means. Taking this holistic view of the world as a starting point , one can describe the state of environmental-health issues in the Latin American and Caribbean region and use that as a guide to facilitate multi-sector arrangements and interventions to improve health.
Throughout the region air pollution, lack of environmental services (water, sewage, and solid-waste treatment), issues of road safety and personal safety, and poor housing are important environmental and social determinants of health. Environmental change in any of these areas will have direct or indirect adverse health effects on populations who contribute little to global changes, aggravating existing health issues whose distribution follows patterns of environmental justice.
The urban environment generally profits most from large-scale investments in the water, sanitation, and waste-management industries, which provide services that considerably improve health. However, maintaining existing systems in the short and long term is still a major challenge in the region. Air quality is another area of concern. Regrettably, air pollution both indoors and outdoors is increasing due to growing problems surrounding transportation and household energy. Because women and children stay at home, these problems affect them disproportionately, and are considered a major source of gender- and age-related inequality. Other urban problems relating to chemicals for domestic use, such as pesticides and cleaning products, and occupational exposures will be analyzed separately in another article. Road safety, violence, and noise are also of immense importance, posing serious physical risks and representing major environmental challenges for those living in cities and other urban settings.
The use of pesticides and other agrochemicals continues to cause significant problems in rural areas. The region consumes large amounts of pesticides, for there is little legislation or regulation on the use of these toxic chemicals. The natural and preserved environments are important sites of biodiversity, but are also implicated in the sylvatic cycles of pathogens like yellow fever, Zika, and others. Those entering such environments or living nearby are at greater risk of exposure to serious and communicable diseases.
Many public-health strategies and actions can be deployed to confront environmental-health problems. These include health promotion (e.g., Healthy Cities and Healthy Parks), inter-sector action (e.g. Health in All Policies), and regulatory and public-policy actions, such as surveillance of sanitation and health.
Addressing the Challenge of a Complex Environment
Understandings of the complex relationship between humans and their physical and social environment has been changing in the 21st century as a consequence of new knowledge that sheds light on aspects related to global changes and the connections between social, physical, and biological surroundings. These developments are challenging traditional public-health concepts and principles. There are many models that try to summarize the different variables in a single indicator, or to present the data in a linear graph; examples include the Human Development Index (HDI) of the UN Development Programme (UNDP, 1990), and the Sustainable Development Index proposed by the Institute for Health Metrics and Evaluation (SDG index) (Fullman et al., 2016). None of these, however, is sufficient to describe and understand the dynamic situation and current trends that are important to public health.
Accordingly, before examining some of the specificities of environmental health in Latin America and the Caribbean, it is important to review the discussions of how human bodies interact with their biological and chemical surroundings, and how creative human minds have altered those surroundings from their “natural” state to a different, human-built environment. It is also important to consider that certain fundamental characteristics of organized societies—such as equity, equal access to services, and environmental justice—determine the distribution, reproduction, and magnitude of the health effects of humans’ interactions with their natural and man-made environments.
The concepts and principles of health and environment vary within countries and between them. While some developed countries focus on the effects on humans and the biological-scientific evidence from the environment, Latin American countries’ attention is directed to understanding the interconnection and social distribution of environmental exposures, and the underlying positions and intervention proposals that inform descriptions and analyses of environmental-health issues.
Conceptual common ground in this area is to be found in questions posed by holistic views and concepts of health that combat the traditional human-centered approach to health focused on medical interventions. The holistic concepts inform a theoretical framework that, without neglecting the medical framework, aims to include other relevant dimensions of the determination process. Such a framework may, for example, include information on global changes, the quest for better distribution of wealth, and innovative technological and political solutions to improve equity and societal relationships.
Last (1997, 2001) proposed a definition of health as “a state of equilibrium between humans and the physical, biological, and social environment, compatible with full functional activity,” capturing some of the analytical challenges in this field of knowledge. This concept proposed an alternative understanding of the very concept of public health as traditionally framed, to focus on the discussion of health as a continuous process produced by determination mechanisms, not just a result of a human-centered process of cause and effect. A similar concern motivated a group of leading scientists to formulate or revisit other concepts, such as “population health” and “planetary health.” These are still being debated, including discussion as to whether they are the same as, or different from, the concept of public health.
“Population health” claims to refer more to the study of health determinants than the diseases that have been the main drivers in public health. Kindig cautioned that discussions of population health “involve many terms, such as outcomes, disparities, determinants, and risk factors, which may be used imprecisely, particularly across different disciplines, such as medicine, epidemiology, economics, and sociology” (Kindig, 2007). “Planetary health” is defined in the final report of the Rockefeller Foundation–Lancet Commission as:
the achievement of the highest attainable standard of health, wellbeing, and equity worldwide through judicious attention to the human systems—political, economic, and social—that shape the future of humanity and the Earth’s natural systems that define the safe environmental limits within which humanity can flourish. Put simply, planetary health is the health of human civilization and the state of the natural systems on which it depends.
(Horton & Lo, 2015)
Any of these three concepts (environmental health, planetary health, and population or community health) would be than what as a lens through which to view the variety of biological, physical, and chemical risks present in Latin America and the Caribbean. Those risks are intrinsic to a complex, interdependent societal reality that determines a non-homogeneous distribution—a distribution that accompanies and reproduces existing societal inequities and injustices, which are responsible for the uneven distribution of acute and chronic effects on populations’ health.
The region’s vast natural forest areas, sea shores, and mountains are home to a precious diversity of animals, micro-organisms, and plants that support life locally and globally. The environmental changes caused by global- and local-scale human activities pose innumerous challenges, some of which, with time, result in definitive changes that ultimately impact health.
Big cities, industry, and the consumption of goods produced locally or imported, sometimes from distant countries, enhance quality of life and provide opportunities, but also pose risks to the natural environment. Also, the population’s unequal social and economic characteristics determine unjust patterns of exposure to many of the risks of everyday urban life, as well as limiting access to such basic environmental services as water, sanitation, and waste disposal, thus increasing the risks and hazards to disadvantaged population groups.
The UN Agenda 2030 and Sustainable Development Goals (SDGs) (UN General Assembly, 2015), adopted by all UN member states in September 2015, lays effective common ground for many health and environment issues, in both their social and their physical dimensions. The document is intended to guide the world on how everyone—local community, country, and the entire community of nations—will collaborate to save the planet and improve its inhabitants’ lives. Health continues to be prominent in this new high-level agreement as a necessary condition and the most valuable outcome of such a large endeavor. But health cannot be achieved by health-sector action alone. The health sector depends on and must collaborate with others. The environment—and its social, biological, and physical dimensions—offers the perfect common ground for collaboration by all sectors to obtain important, feasible, measurable results on the 2030 Agenda. It also serves as a natural means to contribute both to advancing knowledge and to improving planetary health.
As an indication of the magnitude of this challenge, the Institute for Health Metrics and Evaluation (IHME) compiled information to estimate the performance of 33 health-related SDG indicators for 188 countries from 1990 to 2015. It formulated and calculated a designated “health-related SDG index,” which is a function of the 33 health-related SDG indicators proposed by the Inter-Agency and Expert Group on Sustainable Development Goal Indicators (IAEG-SDGs), a group set up by the UN Statistical Commission. It found an improvement from previous years, and in 2015 the median health-related SDG index for the 188 countries was 59.3. Latin America and the Caribbean fall within a cluster of countries in the second-highest quintile of the SDG 2015 Index (62.5–71.5). Figures 3 and 4 give a graphic view of the evolution of overall SDG-index achievement levels from 1990 to 2015.
Table 1. Selected Indicators Related to Health and Environment in the IAEG-SDGs List
Indicator 1.5.1: Age-standardized death rate due to exposure to forces of nature (per 100,000 population)
Indicator 2.2.2b: Prevalence of overweight among children aged 2 to 4 years
Indicator 3.4.1: Death rate due to cardiovascular disease, cancer, diabetes, and chronic respiratory disease among populations aged 30–70 (per 100,000 population)
Indicator 3.5.2: Risk-weighted prevalence of alcohol consumption, as measured by the summary exposure value (SEV) for alcohol use
Indicator 3.6.1: Age-standardized death rate due to road injuries (per 100,000 population)
Indicator 3.9.1: Age-standardized death rate attributable to household air pollution and ambient air pollution (per 100,000 population)
Indicator 3.9.2: Age-standardized death rate attributable to unsafe water, sanitation, and hygiene (WaSH) (per 100,000 population)
Indicator 3.9.3: Age-standardized death rate due to unintentional poisonings (per 100,000 population)
Indicator 3.a.1: Age-standardized prevalence of daily smoking among populations aged 10 and older
Indicator 6.1.1: Risk-weighted prevalence of populations using unsafe or unimproved water sources, as measured by the summary exposure value (SEV) for unsafe water
Indicator 6.2.2: Risk-weighted prevalence of populations using unsafe or unimproved sanitation, as measured by the summary exposure value (SEV) for unsafe sanitation
Indicator 6.2.2b: Risk-weighted prevalence of populations with unsafe hygiene, as measured by the summary exposure value (SEV) for no handwashing with soap
Indicator 7.1.2: Prevalence of household air pollution, as measured by the summary exposure value (SEV) for household air pollution
Indicator 8.8.1: Age-standardized all-cause disability-adjusted life year (DALY) rates attributable to occupational risks (per 100,000 population)
Indicator 11.6.2: Population-weighted mean levels of fine particulate matter smaller than 2.5 microns (PM2.5)
Source: adapted from IASDG Group.
The indicators in the SDG index include many that relate to environmental and occupational health. Table 1 shows a list of selected indicators, reflecting many achievements (such as water and sanitation gains) that need to be secured and some of the major challenges that the region needs to address and improve on, such as air pollution and occupational risks (both included in Agenda 2030), with a window of opportunity of about 15 years. This article will give an overview of these indicators.
Using the IHME tool, it is possible to calculate the variation in environmental and occupational risks (some as in Table 1) as contributors to the “global burden of diseases,” over time and by geographical region and sub-region. As can be seen in figure 5, there have been significant changes in the types of risks faced by the Latin American and Caribbean region. Water, sanitation, and hygiene have seen immense improvements, while air pollution and occupational risks are now the main challenges. These variations are directly associated with disease incidence, as shown in figure 6; diarrhea diseases, for instance, which ranked highest in Latin America and the Caribbean in 1990, are now 27th in the list, mainly because of great improvements in basic sanitation.
Global Environmental Changes and Health in the Latin America and Caribbean Region
Climate change, biodiversity, and desertification are known to have direct and indirect effects on health. The Latin America and Caribbean region’s resource wealth makes it highly vulnerable to any change in the natural environment; this vulnerability is disproportionate to the region’s contribution to the problem, as can be seen in figure 7.
Climate change is linked to many health effects, as shown in figures 8, 9, and 10, proposed by the U.S. Global Change Research program. The health effects and economic consequences projected for the United States can be expected in Latin America and the Caribbean as well.
Water, Sanitation, and Hygiene
One of the most serious problems facing most of the inhabitants of Latin America and the Caribbean, particularly those living in marginalized areas, is the lack of basic public-sanitation services. This situation has ramifications beyond the need to provide safe drinking water and proper sanitation, and touches on the social inequity prevalent in the region (Mújica, Haeberer, Teague, Santos-Burgoa, & Galvão, 2015; Otterstetter et al., 1999).
Lack of drinking water and sanitation impacts on health (fig. 1), and is also related to issues of economic access. Figures 11 and 12 show the correlation between child mortality and access to drinking water. Figure 12 shows differences in water prices as related to the presence of water-distribution systems, which tend to be scarcer in socio-economically less developed areas. The data situates problems of water and sanitation as human-rights issues (Pan American Health Organization, 2011c; UN General Assembly, 2010), as an exclusively technical sanitary approach has proven insufficient to make advances, particularly in sewage management, solid-waste disposal, and hygiene.
In 2001, 589 million people (8.4% of the world’s population) were living in Latin America and the Caribbean, a region historically marked by wide social and economic inequalities: in 2011, annual gross domestic product (GDP) in the countries ranged from US$726 per inhabitant in Haiti to US$10,047 in Mexico, and US$14,394 in Chile. In this context of scarce economic resources, public services in the region, particularly basic sanitation and health, are deficient.
Figure 13 shows that the Latin American and Caribbean region has good baseline conditions for implementation of Sustainable Development Goal 6 of Agenda 2030. Yet even given this optimistic picture of the means, the inequities pose substantial challenges to efforts to reach poor and marginalized areas, as well as efforts to maintain and improve the quality of water, where it is available.
Hygiene practices (fig. 14) are known to be key for maximizing the population-health benefits of access to clean water. The picture here is less positive than for access to safe water sources, and offers a glimpse at how important and inter-sector the problem is: education, for instance, particularly of mothers and young people, has been shown to be an important determinant of the water-borne diseases.
Sanitary disposal of solid and liquid wastes, from both houses and commercial and industrial facilities, is by far the most substantial, expensive, and difficult challenge in achieving the goals of Agenda 2030 on health, water, and urban areas. Figure 15 shows that all countries and regions of the world face challenges in managing sanitation services, and that in Latin America only 22% are safely managed.
Lack of adequate comprehensive sanitation is one of the leading causes of water pollution with domestic and industrial origins. Industrial waste is particularly high-risk, as it may contain carcinogenic, mutagenic, or otherwise toxic chemicals—substances which are normally absent from municipal discharge. Also, improper disposal of untreated solid waste ultimately contaminates both surface water and groundwater (Noyola, Heller, & Otterstetter, 2016).
Noyola et al. (2016) divide water-related diseases into four categories:
a. Diseases caused by drinking water polluted by human, animal, or chemical waste. These include cholera, typhoid fever, shigellosis, giardiasis, dysentery, poliomyelitis, meningitis, hepatitis A and E, and diarrhea, and for the most part can be prevented with proper excreta and wastewater management.
b. Diseases caused by aquatic organisms that spend part of their life cycle in (polluted or clean) water, and part as animal parasites. These diseases, which include dracunculiasis, paragonimiasis, clonorchiasis, and schistosomiasis, are caused by a variety of trematodes, tapeworms, pinworms, and nematodes, collectively known as helminths, which infect humans.
c. Vector-borne diseases associated with water, transmitted by vectors such as mosquitoes, which breed and live near polluted and unpolluted waters, infecting millions of people with diseases that include malaria, yellow fever, dengue, sleeping sickness, and filariasis. The incidence of these diseases appears to be on the rise, among other reasons because the vectors develop resistance to the drugs used to fight them and because climate change is creating new breeding sites.
d. Diseases associated with water shortages and closely linked to the resulting poor hygiene. These include trachoma, tetanus, conjunctivitis, and some skin diseases. These diseases are spreading around the world but can be controlled with better hygiene, for which an adequate supply of clean water is essential.
As show in the Figure 16, water and sanitation has a direct impact on infant mortality which is one of the most relevant health indicators in developing nations. To face such challenge Noyola et al. (2016) made key recommendations for decision makers in the Latin American and Caribbean region. In terms of policy agenda they recommend to promote the positive change that is needed:
• making addressing the lag in sanitation a priority on government agendas;
• Viewing water and sanitation services not simply as a component of infrastructure, but as a civil right whose interdisciplinary and inter-sector relationships must be understood, especially the links with public health, the environment, urban and rural development, and other social policies;
• formulating or adapting public policies to strengthen the sector;
• equipping the local authorities that operate the systems with greater and more effective legal, financial, and technical capabilities;
• establishing regulatory and monitoring frameworks that are efficient and tailored to local conditions;
• promoting organized and informed citizen participation, particularly in rural and marginalized areas;
• developing and implementing comprehensive programs that contribute financing and support to achieve not only greater coverage but also greater operating capacity among the agencies responsible for the services.
In terms of the institutional agenda, Noyola et al. (2016) recommend:
• prioritizing efficient professional management of operating agencies, while shielding them from political vagaries;
• adopting a real user-pay system that includes subsidies for the most disadvantaged users;
• addressing the sustainability of the service through long-term planning, not just new infrastructure;
• developing alternative technologies tailored to conditions in the region (i.e., solutions of its own based on research and development).
Air pollution and climate change are prominent in the WHO’s 13th Programme of Work (WHO, 2018) and were ranked first among the “Ten Threats to Global Health in 2019” listed by WHO in its recent call (WHO, 2019), which explains:
Nine out of ten people breathe polluted air every day, which makes air pollution the greatest environmental risk to health. Microscopic pollutants in the air can penetrate respiratory and circulatory systems, damaging the lungs, heart and brain, and killing 7 million people prematurely every year from diseases such as cancer, stroke, heart and lung disease. Around 90% of these deaths are in low- and middle-income countries, with high volumes of emissions from industry, transport and agriculture, as well as dirty cookstoves and fuels in homes. The primary cause of air pollution (burning fossil fuels) is also a major contributor to climate change, which impacts people’s health in different ways. Between 2030 and 2050, climate change is expected to cause 250 000 additional deaths per year, from malnutrition, malaria, diarrhoea and heat stress.
In October 2018, the WHO held its first ever Global Conference on Air Pollution and Health, in Geneva. Countries and organizations made more than 70 commitments to improving air quality.
Air quality in the Latin American region and elsewhere is known to be associated with respiratory diseases, can cause premature deaths, and costs millions of U.S. dollars in medical care and low productivity. In region’s air-pollution crisis of the 1980s, and subsequent actions taken by the cities of Mexico, Santiago, and São Paulo, are prime examples of the problems countries have experienced from rapid, disorganized urban growth in recent decades, particularly in the largest cities (megalopolises), where air-pollutant levels often exceed national and international limits.
Romieu et al. (2016) estimated that 45,318 people die, and 998,778 life years are lost per year, from urban air pollution across the region. The same study identifies the intensive use of fossil fuels in industry and transportation as being the region’s leading cause of urban air pollution. In the Mexico City Metropolitan Area in 2010, for example, transportation was responsible for 12% of PM10 (particulate matter with a diameter of less than 10 microns), 30% of PM2.5 (particulate matter with a diameter of less than 2.5 microns), 5.06% of sulfur dioxide (SO2), 98% of carbon monoxide (CO), 79% of nitrogen oxides (NOx), 31% of volatile organic compounds (VOCs), 29.6% of toxic pollutants, and 51.4% of carbon dioxide (CO2) emissions.
The effects of air pollution can be seen in Table 2. These are associated with the size and type of contaminants and vary with the type of local pollution. Their identification assists in designing the inter-sector interventions that are needed, involving the health, energy, transportation, and agriculture sectors.
Table 2. Health Effects Associated With Ambient Pollution and Populations at Greatest Risk
Riojas-Rodríguez, Soares da Silva, Texcalac-Sangrador, and Moreno-Banda (2016) found that information on air pollutants was available for only 117 cities in 17 of the 33 Latin American and Caribbean countries. Some 146 million people live in those cities, where annual mean concentrations of inhalable particles were above WHO Air Quality Guidelines, and most had no information on particulate matter of 2.5 microns diameter or less. Therefore, pollutant monitoring and control should be strengthened to protect public health (Riojas-Rodríguez et al., 2016). The air-quality guidelines set out in WHO (2015), the U.S. Environmental Protection Agency’s National Ambient Air Quality Standards (NAAQS), and the AirNow tool (with which a number of countries engage) constitute very useful references for setting standards or targets in the region.
Chemical Substances and Hazardous Waste
Chemicals are everywhere and are essential components of materials in the home, at school, at work, and in entertainment. Our bodies are built on chemical substances, and nutrients and water are chemicals. However, when concentrations (doses entering the live organism) are wrong or in the wrong place, the imbalances can undermine the ways that live beings normally process these substances. It is good and reasonable to drink a glass of water, but is unreasonable and dangerous to drink a glass of water with chemical contaminants such as organic pesticides or arsenic. Medicine and environmental-health interventions use relatively safe chemicals, such as chlorine and some pyrethroids to control or eliminate exposure to pathogenic organisms or to control vector populations. But industry and consumers add thousands of different chemicals in products, or release them into the environment, contaminating air, soil, water, and food. Depending on the kind of chemical and the medium, it can enter the food chain or environmental cycles and reach populations far from the original source of pollution. This is true of DDT, for instance, which has never been used by Inuits, but is present in their bodies (Laird, Goncharov, & Chan, 2013).
Metals such as lead, mercury, and arsenic, volatile organic compounds, and pesticides, are some of the most common chemicals whose health effects have been clearly identified. They are also present in what is called hazardous waste. The Glossary of the U.S. Agency for Toxic Substances and Disease Registry (ATSDR) defines hazardous waste as “Potentially harmful substances that have been released or discarded into the environment.” This broad definition includes any chemical compound, element, or combination thereof that enters the environment through improper use, treatment, storage, transport, or disposal, and there—because of its quantity, concentration, or physical or toxicological properties—poses a hazard either to the environment or to human health. The website of the U.S. Environmental Protection Agency (EPA) stresses that hazardous wastes are dangerous or potentially harmful to health or the environment, and can be found as liquids, solids, gases, or sediments.
Hazardous wastes are complex mixtures and require particular handing; classification and a medium-to-long-term program are essential to address the problems they pose. Câmara et al. (2016), citing the EPA classification of hazardous wastes, divided them into 4 categories: a) ignitable (i.e., wastes that, under certain conditions, produce spontaneous combustion); b) corrosive (i.e., acids and bases—pH ≤2 or ≥12.5); c) reactive (i.e., wastes that are unstable under normal conditions or can explode or emit fumes, gases, or vapors when heated, compressed, or exposed to water); and d) toxic (i.e., wastes that can cause acute or chronic poisoning and death). Biological and radioactive waste, generated mainly by health facilities such as hospitals, clinics, and research laboratories, is of special interest to the health sector, not only for action, but also as it is the sector itself that produces and needs to control it.
Pollution by chemicals occurs in association with production processes that modify the environment and, consequently, populations’ health profiles. Pollution by chemicals occurs in association with production activities that manipulate nature to economic and social ends, modifying the environment regardless of its ability to survive and, in the process, altering population health profiles regardless of the limits on human survival (Tambellini, 1996). These production and consumption processes, in which people transform raw materials into goods through their ability to work and use tools and instruments, involve the acquisition and transportation of raw materials, processing of the raw materials into goods, consumption of the goods, and, finally, generation of waste. Note that waste is generated at all stages of these processes and not just in the final consumption stage.
Schemes to address this highly complex problem aim to order and systematize the process, from its initial identification to monitoring its health consequences in exposed populations. Figure 17 represents one example of practice in the region.
Chemicals are not a new problem, nor are they problematic only when they build up in the environment. Each chemical element, substance, or mixture is per se a potential contaminant, sometimes even in very small quantities. Philippus Aureolus Theophrastus Bombastus von Hohenheim (known as Paracelsus, 1493–1541) wrote, “All substances are poisons; there is none which is not a poison. The right dose differentiates a poison from a remedy.”
Figure 18 (WHO, 2010) identifies 10 chemicals of major public-health concern, listing some of the most common pollutants. Exposure to any of these chemicals, or a mixture of them, can have acute or chronic effects that impact population health. Figure 19 (WHO, 2016) shows the exposure process and the many ways public-health initiatives can ameliorate or prevent its effects.
Chemical pollution is a common cause of harm to other living organisms and is not likely to go away in the near future. The graph in figure 20, showing chemical-production trends up to the middle of the 21st century, shows a clear tendency for production to increase.
The impact of pesticide use on human health is a relatively well-documented problem. It has been addressed in different ways by Latin American and Caribbean scientific communities, especially in developing countries where these chemicals are used in agriculture with little control. Developing countries account for 30% of the global pesticide consumer market, and Brazil is the largest individual consumer market, accounting for half of all Latin American pesticide consumption (Peres, Moreira, & Luz, 2007). The pesticide types and conditions in which they are used in the Latin American region result in environmental pollution and human poisoning. Peres et al. (2007) found that many farmers are unaware of the hazards associated with pesticide use, and thus neglect basic health and occupation safety standards. This has resulted, in Brazil, in human contamination levels ranging from 3% to 23%. If the lowest percentage in the range (3%) is applied to the number of rural workers involved in ranching and farming activities in Brazil (estimated at around 18 million in 1996), the approximate number of individuals contaminated by pesticides while engaged in work activities in Brazil would be around 540,000 per year, with 4,000 deaths.
In the same study, Peres et al. mentioned factors that aggravate the situation, such as: low education levels; lack of effective technical monitoring or counseling policies; aggressive marketing and sales practices by pesticide-industry producers and distributors; lack of familiarity with successful alternative pest-control techniques; careless pesticide waste and package disposal; continued use of an exposure to pesticides; highly technical content of educational material available to rural populations; communication difficulties between farmers and technicians; failure on the part of governments to provide farmers with effective continued and technical assistance; and lack of effective government-control strategies on pesticide selling.
Cocco (2016) examined pesticides and human health in detail, acknowledging that about 100,000 different inorganic and organic chemicals were then on the market, and grouping them according to their purpose, as insecticides, herbicides, fungicides, fumigants, rodenticides, fertilizers, growth regulators, etc., or their chemical structures, as organochlorines, organophosphates, pyrethroids, carbamates, dithiocarbamates, organotin compounds, phthalimides, phenoxy acids, heterocyclic azole compounds, coumarins, etc. Cocco also acknowledges the problem of runoff of these substances into the environment, and the problem of organochlorine persistence, leading to accumulation in the food chain.
The U.S. Environmental Protection Agency (EPA) publication Recognition and management of pesticide poisonings (Roberts & Reigart, 2013) offers a great deal of information about the occurrence of poisonings and appropriate clinical treatment. There are many similar publications in developed countries that are extremely helpful to practitioners and researchers. Environmental and socio-economic conditions in middle- and low-income countries are different, however, and although there are many publications that translate and endeavor to adapt information for local realities, more research is needed in order to understand better the interactions between pesticides and local conditions in those countries. Cases of suspicious relationships between pesticides and a variety of effects ranging from renal failure (Valcke, Levasseur, Soares, & Wesseling, 2017) to suicides (Faria, Fassa, & Facchini, 2007) have been reported in the Latin American and Caribbean literature, and there is much potential for further research and maybe breakthroughs regarding the relationship between chemicals, environment, and human health.
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