Key points

Introduction

Children today live in a world with increasing exposure to environmental hazards. Environmental stressors have increased as the world’s population has increased from 2.5 billion in 1950 to 7 billion today. A global trend toward urbanization is further accelerating children’s exposures to environmental hazards, especially in the world’s poorer countries. By 2050, it is projected that 66% of the world’s population will reside in cities.

Environmental pollution in both urban and rural settings has become a major cause of disease in children. Along with traditional hazards of indoor air pollution and contaminated drinking water, children today are exposed to newer environmental threats such as urban air pollution, global climate change, toxic industrial chemicals, pesticides, heavy metals, and hazardous wastes. All of these global environmental changes have major implications, positive as well as negative, for the health of children.

The World Health Organization (WHO) estimates that 17% of deaths of children in developed nations are attributable to environmental exposures compared with 24% in developing nations. Environmental exposures result in more deaths (adults and children) than are caused by human immunodeficiency virus (HIV)/AIDS, tuberculosis, and malaria combined. The diseases caused by traditional forms of environmental pollution (eg, coliforms in water or air pollution from solid fuels) are predominantly diarrhea, pneumonia, and other infectious diseases. Modern environmental threats, by contrast, are linked mainly to chronic diseases: asthma, neurodevelopmental disorders, birth defects, obesity, diabetes, cardiovascular disease, mental health problems, and pediatric cancer. Children in rapidly industrializing countries are simultaneously confronted by both ancient and modern environmental threats to health.

In an ever more interconnected world, pediatricians need to be aware of current environmental threats to children’s health, locally as well as globally. Highly toxic pesticides no longer permitted in the United States are still used in countries around the world and can expose North American children who eat imported fruits and vegetables. Recent immigrants bring hazards from their home countries such as lead-contaminated cosmetics or medications containing mercury. Children adopted from foreign countries may have been exposed prenatally or during early childhood to chemical hazards more common in their country of origin. Awareness of hazards such as these and openness to the discovery of new environmental threats to children’s health will enhance pediatricians’ ability to diagnose, treat, and prevent disease in children.

Introduction

Children today live in a world with increasing exposure to environmental hazards. Environmental stressors have increased as the world’s population has increased from 2.5 billion in 1950 to 7 billion today. A global trend toward urbanization is further accelerating children’s exposures to environmental hazards, especially in the world’s poorer countries. By 2050, it is projected that 66% of the world’s population will reside in cities.

Environmental pollution in both urban and rural settings has become a major cause of disease in children. Along with traditional hazards of indoor air pollution and contaminated drinking water, children today are exposed to newer environmental threats such as urban air pollution, global climate change, toxic industrial chemicals, pesticides, heavy metals, and hazardous wastes. All of these global environmental changes have major implications, positive as well as negative, for the health of children.

The World Health Organization (WHO) estimates that 17% of deaths of children in developed nations are attributable to environmental exposures compared with 24% in developing nations. Environmental exposures result in more deaths (adults and children) than are caused by human immunodeficiency virus (HIV)/AIDS, tuberculosis, and malaria combined. The diseases caused by traditional forms of environmental pollution (eg, coliforms in water or air pollution from solid fuels) are predominantly diarrhea, pneumonia, and other infectious diseases. Modern environmental threats, by contrast, are linked mainly to chronic diseases: asthma, neurodevelopmental disorders, birth defects, obesity, diabetes, cardiovascular disease, mental health problems, and pediatric cancer. Children in rapidly industrializing countries are simultaneously confronted by both ancient and modern environmental threats to health.

In an ever more interconnected world, pediatricians need to be aware of current environmental threats to children’s health, locally as well as globally. Highly toxic pesticides no longer permitted in the United States are still used in countries around the world and can expose North American children who eat imported fruits and vegetables. Recent immigrants bring hazards from their home countries such as lead-contaminated cosmetics or medications containing mercury. Children adopted from foreign countries may have been exposed prenatally or during early childhood to chemical hazards more common in their country of origin. Awareness of hazards such as these and openness to the discovery of new environmental threats to children’s health will enhance pediatricians’ ability to diagnose, treat, and prevent disease in children.

Air

Air pollution is a complex mixture of gases, particles, and aerosols, and results from mobile sources, industrial facilities, home heating and cooking, and natural sources such as wildfires. The intense smog episodes in London in 1952, and similar episodes elsewhere, resulted in a large spike in deaths from cardiovascular and respiratory disease. Since then, air pollution epidemiologists have identified many adverse health outcomes in both children and adults. Particulate matter (PM), also known as particulate air pollution, especially finer ambient particles, can penetrate deeply into the respiratory tract and is associated with cardiovascular morbidity and mortality in adults. Ozone, nitrogen oxide (NOx), and other pollutants are similarly associated with increased mortality and morbidity.

The fetus, infants, and children are particularly susceptible to adverse effects of air pollution due to rapid cell division, differentiation, and the high demand for oxygen and nutrients to support growth. Studies report associations between air pollution, especially PM2.5 (≤ 2.5 microns in diameter), and adverse birth outcomes, including

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  Lower birth weight, intrauterine growth retardation, and preterm birth

  
  
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  Birth defects (mixed results)

  
  
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  Infant mortality (postneonatal respiratory infection).

Researchers studying a cohort of children in southern California have demonstrated associations between reduced lung function growth and regional and traffic-related air pollution, including PM2.5, NOx, and ozone. Reduced lung function at age 18 years is irreversible because lung function growth has stopped by that age. Compromised lung function in early adulthood is associated with risk for premature mortality and other adverse health outcomes throughout adult life. A meta-analysis conducted by the Centers for Disease Control and Prevention (CDC) found traffic exposure in childhood to be associated with a 50% increase in childhood acute lymphoblastic leukemia. Other studies have implicated traffic in risk for germ cell tumors and retinoblastomas in children. In 2013, the International Agency for Research on Cancer (IARC) identified air pollution and PM as known human carcinogens based on sufficient evidence of lung cancer in adults. Finally, research has shown associations between air pollution and adverse neurodevelopmental effects in children.

Many studies have reported associations between regional and traffic-related air pollution, including diesel exhaust, and exacerbation and induction of asthma.

Many governmental organizations have set standards for components of air pollution that serve as goals and promote innovation in pollution controls ( Table 1 ). In the United States, both the California Environmental Protection Agency (EPA) and the US EPA have used considerable resources implementing regulatory actions to reduce air pollution. These efforts have paid off in terms of improving children’s health. Investigators report improved lung function growth in successive cohorts of children in southern California as air quality has improved. Improvements in 4-year lung function growth during childhood, measured by forced expiratory volume (FEV)-1 and forced vital capacity (FVC), have coincided with lower ambient exposures to both NOx and PM pollution. The proportion of children with clinically significant decrements in lung function at age 15 years declined from 7.9% to 3.6% from the mid-1990s to 2011. Previously, these investigators had shown that children who moved from a high pollution area to a lower pollution area experienced improvement in lung function growth. Clearly, regulations that reduce air pollution can be effective and result in health improvements for children. Regional, national, and global improvements are needed.

Airborne pollutants are transported around the world and can affect the health of children far from their point of origin. Industrial and traffic emissions from Asia add to exposures in the western United States; airborne particulate pollution from coal-burning power plants in the Ohio Valley adversely affect children on the east coast of the United States.

Low- and middle-income countries (LMICs) are experiencing large increases in exposures to urban air pollution due to increased combustion of coal and other fossil fuels for industrial activities, as well as increasing car ownership. Globally, 88% of urban residents live in cities that fail to meet WHO air quality guidelines. The WHO compiles information on particulate matter concentrations from more than 1000 cities around the globe ( Table 2 ). This information indicates that LMICs generally have more particulate air pollution and, by inference, other air pollutants than high-income countries (HICs). Thus, children in LMICs are at much higher risk of adverse respiratory health effects from air pollution. Further, indoor air pollution can be very high in homes using biomass for cooking with inadequate ventilation. WHO attributes 334,000 deaths of children to household air pollution and 127,000 to outdoor air pollution worldwide annually, mostly from lower respiratory infections. Efforts to reduce both indoor and outdoor air pollution globally are warranted.

Worldwide, 3 billion people use indoor, inefficient, solid fuel cookstoves or fires that cause more than 1.9 million deaths annually and are the fourth largest health risk in the developing world. The Global Alliance for Clean Cookstoves is a public–private partnership working to get 100 million households to adopt clean and efficient cookstoves by 2020 ( Box 1 ). Helping a community transition to clean and efficient stove technologies will help improve immediate and long-term health and reduce production of greenhouse gases.

Water

In North America, drinking water generally presents a low risk for microbial infection due to engineering for hygiene. Federal and state agencies set standards for chemical contaminants of concern, including chemicals that affect infants and children, such as nitrates (methemoglobinemia), perchlorate (inhibition of iodine uptake by the thyroid), and lead (neurodevelopmental delay). Information pertaining to drinking water standards can be obtained online (see Box 1 ). Large water systems are routinely monitored in the United States but private wells serve a many people and are not monitored for contaminants. Emerging concerns include pharmaceuticals in drinking water, climate change–associated water quality and scarcity issues, and region-specific contaminants, including arsenic and radionuclides.

In many LMICs, availability of clean drinking water is among the most acute environmental health needs. Different strategies have been effective in different circumstances. New York City has used extensive watershed protection to maintain quality while reducing expenses by limiting the need for additional expensive water treatment. This model is being used to protect urban water systems in projects around the world (see Box 1 ). Where there are no sanitary water systems, other novel approaches have been successful. More than 5 million people in 50 countries use solar disinfection (SODIS) to improve water quality and decrease diarrheal diseases. Plastic bottles (polyethylene terephthalate [PET]) are filled with low turbidity water and placed in the sun for 6 to 48 hours (depending on weather). Ultraviolet-induced DNA alteration, thermal inactivation, and photo-oxidative destruction inactivate disease-causing organisms. Studies have demonstrated 9% to 86% reductions in diarrheal diseases. Training and technical support for implementing SODIS programs are available (see Box 1 ).

Pesticides

More than 700 pesticide chemicals, including insecticides, herbicides, rodenticides, and fungicides, are currently registered with US EPA. These are chemicals deliberately engineered to kill or repel living things and thus have inherent toxic potential.

Synthetic pesticides introduced after World War II are now ubiquitous. A 2000 US EPA survey demonstrated that 74% of US households use 1 or more pesticides around the home. Over time, insecticide use has evolved from chlorinated compounds such as dichlorodiphenyltrichloroethane (DDT) to organophosphates (OPs) and, more recently, pyrethroids. Though having low acute toxicity, organochlorine pesticides are persistent and associated with chronic health concerns. In making the switch to the OPs, we have substituted for the acute and neurodevelopmental toxicity of OPs. Due to regulatory actions based on demonstrated neurocognitive impacts, since the early 2000s, residential use of OPs has largely been replaced by pyrethroids. Initial concerns about pyrethroids being associated with allergic reactions have been accentuated with recent studies suggesting possible impacts on neurodevelopmental delay, autism, and male reproductive health.

Newer, designer, pesticides have been introduced in recent years that target physiologic systems of insects and plants with the assumption that they would likely not have effects on human health. A prominent example is the neonicotinoid pesticides that target nicotinic acetylcholine receptors, which are different in insects than mammals. There are few epidemiologic studies of the health impacts of these chemicals (used in agriculture and as flea and tick pesticides for pets) on humans though limited evidence has suggested a possible impact on neurodevelopment.

Pesticides may have developmental impacts via mechanisms distinct from their pesticidal action, as has been demonstrated for the organophosphate chlorpyrifos.

Glyphosate, the herbicide with greatest use worldwide, was long considered a relatively innocuous pesticide. But in 2015, based on new evidence of carcinogenicity from both animal studies and epidemiologic investigations, the IARC identified glyphosate as “probably carcinogenic to humans.” Understanding of the health hazards associated with chemical exposures changes with evolving science.

In 2011, acute poisoning incidents from pesticides were responsible for more than 39,000 calls to poison centers in the United States. An excellent manual, Recognition and Management of Pesticide Poisonings , is available from the US EPA online, in English and Spanish. Low-dose exposures to certain pesticides during pregnancy and childhood are associated with increased risk for attention problems, lower intelligence quotient (IQ), behavioral changes, and pervasive developmental delay, altered brain architecture, asthma and respiratory symptoms, and childhood leukemia.

Though OP pesticides have largely been banned for residential use in the United States, they continue to be used in agriculture and their residues are found on food. Pesticide residues (eg, OPs and herbicides) on food contribute significantly to exposure in children, even those living in agricultural communities. Consumption of fresh fruits and vegetables is a priority for children, thus selection of organic products should be weighed against their cost and availability. Nonetheless, the evidence of health effects from low-dose exposures to some pesticides indicates a need to reduce developmental exposure to pesticides as much as is practical. In 2012, 4.7% of imported and 0.9% of domestic foods sampled contained residues greater than allowable in the United States. Some of the pesticides found on imported foods are not registered for use in the United States. Some products had high rates of unallowable residues. For example, more than 40% of imported Basmati rice was in violation. The Environmental Working Group uses federal agency data to determine fresh produce that has high (dirty dozen) and low (clean 15) pesticide loads. Those concerned about exposure can use these aids in determining which produce might be preferable.

Residential use of pesticides is a major contributor to exposure. Integrated pest management (IPM) is an approach to minimizing pesticide use in residential, school, and agricultural settings. It integrates chemical and nonchemical methods to provide the least toxic control of pests. IPM has proven to be cost-effective and, at times, more effective at long-term control of pests while reducing pesticide exposure. Unfortunately, adoption of IPM methods in LMICs has lagged behind that of HICs.

Several billion pounds of pesticides are used annually worldwide, less than one-quarter of that in the United States. The production and export of obsolete and persistent pesticides from developed to developing nations, though still a problem, has improved with international agreements and guidance. These documents provide information and tools useful for health care workers in addressing public health and are well summarized in International Tools for Preventing Local Pesticide Problems (see Box 1 ).

Whether in the United States or abroad, appropriate and safe use of pesticides depends on education and training of the workers or community members using them. Children have been exposed when parents bring contaminated clothing home, use agricultural pesticides from work at home, use empty containers to hold water or food, and when children work in fields or apply pesticides. In many nations, pesticides are used in a setting of illiteracy and limited safety training. Health care providers working in developing nations should be able to recognize and treat pesticide poisoning. They can provide education on the health effects of pesticides and how to prevent exposure. Sources such as A Community Guide to Environmental Health can help with simple low-literacy approaches to improving community health and can include pesticide education. Both acute and chronic low-level exposures have resulted from misuse as well as careless use and accidents. Contamination of water, soil, housing, and food with current and obsolete pesticides is not rare. Often, old obsolete pesticides have been stockpiled and inadequately stored (at times degrading to more hazardous material) in developing nations. Information on obsolete pesticide management is available from the United Nations and nongovernmental organizations (NGOs) such as ObsoletePesticides.net (see Box 1 ).