Environmental Burden of Disease Assessment

The environmental burden of disease assessment approach described in this volume is illustrated through its application to the United Arab Emirates (UAE). The UAE occupies 83,600 km² along the Arabian Gulf, with an estimated 2011 population of about 7.5 million. The UAE supports a diversified modern economy and, as a result, faces environmental and public health problems similar to those of other industrial nations. The methods we illustrate build upon a series of guidelines on environmental burden of disease assessment published by the World Health Organization beginning in 2003. Although many countries have employed these guidelines to assess the burden of disease due to individual environmental risk factors, the comprehensive environmental burden of disease assessment across multiple exposure pathways and contaminants described in this book is the first of its kind. This project was intended to serve as a model for other nations wishing to conduct similar assessments. The basic methods can be applied to any nation or subnational geographic unit (such as a state or city). Furthermore, much of the information on relationships between exposures to pollutants and the probability of becoming ill is, and will increasingly be, relevant across the globe. These relationships are specified in the UAE Environmental Burden of Disease Model, a multilayered computer simulation tool constructed in Analytica software. Other countries can adopt this model’s structure, along with much of the input data, as a starting point for their own environmental burden of disease assessments. Also relevant to other nations is the process we used to prioritize risks to include in this analysis—a process that involved systematic consultations with environment and health stakeholders. Other nations can save considerable time and resources in carrying out similar assessments by using the approaches and modeling methods described in this book.

This chapter discusses in detail the process we used to engage stakeholders in further refining the scope of issues to consider in this environmental burden of disease assessment. First, we provide background on innate human cognitive biases that affect our perceptions of risk and how these biases pose challenges to rational priority setting. Then, we describe previous international experiences in prioritizing environmental risks to health for policymaking. Next, we describe the systematic approach used here to prioritize environmental risk factors—an approach that compensates for cognitive biases, incorporates scientific information, systematically involves multiple stakeholders, and builds on international experiences. Finally, we describe how we implemented this ranking process and how the results led to the eight environmental risk factor categories that are the subjects of the remaining chapters of this book: outdoor air pollution, indoor air pollution, occupational exposures, climate change, drinking water contamination, coastal water pollution, soil and groundwater contamination, and produce and seafood contamination.

The purpose of environmental burden of disease (EBD) studies is to assess what fraction of the global, national, or regional burden of disease is attributable to selected environmental risks, using an explicit, widely recognized methodology. The method used to estimate the EBD in the United Arab Emirates is based on a method developed in the 1990s by the World Health Organization in the first global burden of disease study. The approach is based on determining the attributable fraction—the proportion of death or disability attributable to a specific risk (e.g., air pollution) or health condition (e.g., high blood pressure). To estimate the environmental burden of disease in the UAE, the research team that conducted this study constructed an innovative computer model, the UAE Environmental Burden of Disease Model, coded in Analytica software. The model, the first of its kind, is designed to facilitate comparing the importance of different risks and testing the effects of various environmental interventions on the UAE’s overall disease burden. The model is divided into subcomponents, each corresponding to one of the eight environmental risk areas retained for analysis as a result of the priority-setting exercise described in Chap.​ 2. This chapter describes the principles underlying the model, based on steps including exposure assessment, determination of the exposure-­response relationship, estimation of mortality and morbidity, calculation of the attributable fraction, determination of the disease burden attributable to the risk, and uncertainty and sensitivity analysis. Estimation of the burden of disease in the UAE with an easy-to-understand computer model is a state-of-the-art method for analyzing the fragmentary data that were available on the disease distribution in the UAE and for communicating the results effectively. This innovative model allows comparison of the relative importance of various sources of ill health and examination of the effects of alternative interventions on the disease burden. The model also makes it very easy to update future burden of disease estimates when new data become available, and it allows UAE officials to test the effect of various intervention options. Because all assumptions, decisions about input variables, and specific methods are clearly stated in each step, changes to the model structure can be made easily should future research and new data prove it necessary. Because resources are always limited, the model can facilitate identification of the most important risks and prioritize competing actions to recognize the ones with the greatest potential to reduce the burden of disease.

Anthropogenic outdoor air pollution caused a substantial number of premature deaths in the United Arab Emirates in 2008, and this mortality number is estimated to be the greatest among the eight priority environmental risk areas in this book. In this chapter we quantify the burden of disease, including premature deaths and health-care facility visits, associated with outdoor air pollution, specifically ambient particulate matter (PM) and ozone from anthropogenic sources, and we discuss the uncertainties associated with the estimates. The negative impacts of PM and ozone on public health have been well documented, particularly the mortality effect of PM. For morbidity, scientific studies have linked exposure to PM and ozone to a variety of health problems, particularly respiratory and cardiovascular diseases. Two different approaches were used to estimate outdoor PM and ozone concentrations across the UAE: the measurement-based approach and the air-­quality-model-based approach. The measurement-based approach relies on data from 10 fixed monitoring stations in Abu Dhabi emirate. The model-based approach uses Community Multiscale Air Quality modeling software to predict air quality based on estimates of air pollutant emissions and meteorological conditions. Using the measurement-based approach, this research estimates that in 2008 the total number of premature deaths in the UAE caused by exposure to ambient particulate matter was approximately 650. These account for about 7% of the total deaths occurring in the UAE in 2008. About 77 deaths were attributable to ground-level ozone in 2008. With respect to excess illness, in 2008 PM₁₀ exposure caused a mean estimate of 15,000 health-care facility visits for respiratory and cardiac illnesses, accounting for about 3% of total medical visits. Ground-level ozone caused a mean estimate of 9,800 respiratory health-care facility visits in 2008, accounting for about 6% of total respiratory health-care facility visits in that year. Thus, in total, PM appears to cause a larger disease burden in the UAE than ozone. Using the CMAQ model-based approach, the estimated death numbers attributable to PM were smaller than the measurement-based estimates, whereas the estimated death numbers attributable to ozone are greater than those using the measurement-based approach. Also, the estimated health-care facility visits attributable to PM are smaller than the measurement-­based estimates.

Indoor air pollution has evolved into a high-priority risk across the globe, with various organizations ranking indoor air pollution in the top category of environmental risks. Indoor air pollutant concentrations are a function of indoor source emissions, the infiltration of ambient pollution via building leakage, and the air exchange rate (ventilation) in the building. Health effects range from acute conditions such as sensory irritation to chronic, potentially life-threatening conditions such as cancer and cardiovascular disease. The three primary factors that affect indoor air quality are the nature of indoor pollutant sources, ventilation of the building, and occupant behaviors. This initial modeling effort focuses on the residential environment because people spend the majority of their time indoors in residential dwellings. Deficient air quality can exist in all types of enclosed buildings and structures. In the future, the methods and models developed here could be applied to other indoor environments. The burden of disease due to a particular pollutant was calculated by multiplying the attributable fraction by the observed number of cases of the relevant health outcome in the population. The leading source of indoor air pollution contributing to excess cases of illness is environmental tobacco smoke. Altogether, it appears to cause more than 80% of the health-care facility visits attributed to indoor air pollution. The leading health outcomes attributed to indoor air pollution are cardiovascular disease and lower respiratory tract infections. An estimated 280 deaths result from those diseases, with approximately 88% of those deaths attributed to cardiovascular disease caused by environmental tobacco smoke. Our analyses suggest that indoor air pollution is a considerable risk to public health in the United Arab Emirates (UAE), accounting for at least 77,000 excess visits to health-care facilities in 2008 in addition to the 280 excess deaths. In terms of mortality, indoor air quality ranks second only to outdoor air pollution as a cause of environmentally related diseases in the UAE.

Workers may be exposed to physical, chemical, and biological hazards at work that may lead to occupational illness. Hazardous substance exposure routes include dermal and inhalation exposure and ingestion. Families of workers also can face risks from toxic substances brought home on contaminated work clothes or vehicles. This chapter estimates occupational exposures to harmful chemicals and noise in the United Arab Emirates (UAE) and calculates the burden of disease related to selected occupational hazards. Occupational health studies conducted in the UAE have revealed unsafe work practices and unhealthy working conditions in many industry sectors, but the majority of UAE workers who are potentially exposed to hazardous substances and noise are employed in construction, agriculture, or manufacturing. The exposures covered in this study were selected following the approach by the World Health Organization, covering common occupational carcinogens, occupational airborne particulates, and noise, excluding occupational injuries and ergonomic stressors. The estimated total number of annual deaths due to health outcomes included in this study is 47, and the total number of health-care facility visits is 17,160. In addition, the model estimates that 4,770 cases of noise-induced hearing loss occur due to occupational exposures each year. Of the health outcomes covered in the study, lung cancer and leukemia were responsible for the highest number of deaths (25 and 12, respectively). For health-care facility visits, asthma and chronic obstructive pulmonary disease contributed most to the disease burden with 11,854 and 5,012 visits, respectively. It is likely that the UAE could reduce the amount it spends on medical care by reducing exposure to respiratory irritants, carcinogens, and noise in workplaces. These numbers should not be considered to represent the total disease burden arising from all occupational exposures. Many prevalent occupational hazards, such as injuries and ergonomic stressors, were excluded because this study focuses on health risks due to releases of hazardous physical, chemical, and biological agents into the environment as a result of human activities.

Expected climate change may be particularly important in the United Arab Emirates (UAE) due to its already hot and arid climate. Compared with other nations, the UAE has a relatively low level of total greenhouse gas (GHG) emissions, with an estimated 0.31–0.42% of global emissions since 1994. However, the UAE has one of the highest levels of GHG emissions per capita, consistently ranking second or third in the world over the past two decades. Climate change is likely to have only limited impacts on infectious and diarrheal diseases in the UAE due to relatively low baseline levels of these climate-sensitive diseases. The major impacts of climate change in the UAE are expected to be increased heat stress and possibly increased water- and vector-borne diseases, as well as decreased water availability and food production. The total burden of disease from climate change is inherently difficult to determine due to the many mechanisms through which climate can affect public health and the high level of uncertainty with future climate scenarios, GHG emission levels, and human adaptation measures. Our model includes only the effect of climate change on cardiovascular disease. The results show that climate change currently has minimal effects on human health relative to the other modeled priority areas. There were approximately 410 additional health-care facility visits and three additional deaths from cardiovascular disease in the UAE in 2008 due to the added risks of climate change.

The Gulf Coast countries, including the United Arab Emirates (UAE), have the lowest supplies of fresh water per capita in the world. The groundwater extraction rate has become unsustainable, and desalinated water has become the main source of drinking water, either through piping (tap water) or as bottled water in the UAE. The product water from desalination is generally of high quality but may contain some contaminants, including microbial contaminants, chemicals that may cause acute illness, chemicals that may cause cancer, and radiological contaminants. Chemical disinfectants destroy microbes and prevent their growth in water, but they also produce unwanted chemical by-products that could affect health, including by causing cancer. Water traveling from the desalination plant can be recontaminated within the distribution system via infiltration, corrosion, and bacteria associated with biofilms. Past intermittent service and concerns about having sufficient water in the event a major desalination plant is taken offline due to a technical issue, oil spill, or hostile act have led to the widespread use of rooftop and in-ground storage tanks. These vented tanks are often outdoors and are subject to high temperatures, intense sunlight, animal activity, and windborne contaminants. It is unclear how well these tanks are cleaned and maintained. Our model focuses on the health effects of microbial contamination and disinfection by-products. Drinking water quality data at the point of use for the UAE could not be found, which made it necessary to rely on data from the published literature on samples from Kuwait. Comparisons of water quality data from water treatment plants and distribution networks in Kuwait and Abu Dhabi suggest that Kuwaiti data on water quality at the consumer’s tap are a reasonable proxy for Abu Dhabi tap water quality. Data collected by the Abu Dhabi Distribution Company and provided for this study for comparison to Kuwaiti data included 471 samples from 79 stations at endpoints in the distribution system sampled throughout 2008. Based on this assessment, the burden of disease attributable to drinking water in the UAE appears to be small, with a mean estimate of 12 deaths from all causes. This study estimates 340 health-­care facility visits each year due to drinking-water-related cancer and 46,000 visits due to gastroenteritis.

Soil and groundwater contamination due to waste disposal may pose an increasing public health threat in the United Arab Emirates (UAE) if measures are not taken to improve waste management practices and prevent exposure to wastes disposed of improperly in the past. The UAE currently has one of the highest rates of solid waste generation per capita of any country in the world. In addition, waste disposal in the UAE historically has been inadequately controlled, with wastes of a wide variety disposed of in open, unlined dump sites in the desert. Chemicals can leach from uncontrolled waste disposal sites and contaminate soil and the underlying groundwater. The soil in much of the UAE is silty and sandy with low cation exchange capacity. This soil type is highly permeable, and thus contaminants that leach from waste sites have the potential to migrate rapidly and contaminate large areas. At the time this project was carried out, no data were available on the nature and amounts of hazardous chemicals found in soil and groundwater in the UAE from waste disposal sites, but the types of chemicals present due to releases from waste disposal sites are likely to be similar to those found in groundwater contaminated from past waste disposal practices in other developed countries. These chemicals are associated with a range of effects, from cancer to neurological and reproductive effects to suppression of the immune system. Current information is not sufficient to assess the burden of disease due to soil and groundwater contamination from waste sites in the UAE. At present, this disease burden is likely to be small because of the small size of the potentially exposed population. However, given the plans to invest in developing the Western Region, it would be prudent for the UAE to begin to collect the information needed to assess risks from these sites to the current population and to future residents. Our primary recommendation is a two-part process that first would provide approximate estimates of the potential burden of disease from individual waste disposal sites and then develop detailed risk assessments for sites showing a significant health risk potential. The information needed for the first part of this process should be relatively easy to obtain, with the primary effort required for additional visual inspections of a selected number of waste sites. Once these basic site inspections and preliminary risk assessments are completed, the UAE government will have greatly improved estimates of which waste sites may be cause for concern, allowing it to focus on sites that have significant risk potential.

Eating fruits and vegetables is beneficial to human health but exposes people to risk if the produce contains hazardous contaminants. Two potential contaminants are human pathogens (e.g., Salmonella, E. coli) and agricultural pesticides (e.g., organophosphates, carbamates), both of which can be reduced with proper food handling and preparation. Foodborne pathogens can cause and/or contribute to an array of human illnesses, including acute gastroenteritis as well as more complex chronic conditions such as organ failure, arthritis, and heart disease. Agricultural pesticide exposure can result in dizziness, nausea, abdominal cramps, diarrhea, tremors, anxiety, confusion, neurological disorders, developmental/reproductive disorders, and death. Because large percentages of fruit, vegetables, grains, and legumes consumed in the United Arab Emirates are produced abroad, pesticide use and other farm management practices in countries exporting to the UAE will affect contamination levels of food consumed in the UAE. Domestically harvested seafood has historically been a primary staple of the Emirati diet. More than 90% of citizens eat fish during at least one meal every week. Consumption of fish provides numerous documented health benefits, including a reduction in risk of chronic heart disease; however, fish can also serve as a vector for pathogenic microorganisms (e.g., Vibrio spp.), heavy metals (e.g., mercury) and other toxins (e.g., dioxin). Estimates of illness resulting from seafood consumption focus on exposure to mercury. Although numerous metals can result in adverse health effects if consumed in seafood, mercury is generally regarded as of greatest concern. Chronic mercury poisoning results in a host of neurological and psychological symptoms, including tremors, motor/cognitive dysfunction, and memory loss. Exposure in utero can result in serious lifetime illness, including mental retardation, sensory loss, developmental delay, cerebral palsy, and seizures. In lieu of estimating foodborne mortality and morbidity cases, our modeling approach directly calculates the probability of exceeding international guidelines for exposure to specific hazardous chemicals in fruit, vegetables, and seafood in the UAE. For fruits and vegetables, the model estimates the number of daily incidents in which UAE residents are exposed to a particular type of pesticide residue above a prespecified benchmark dose, due to eating a particular type of fruit or vegetable. For seafood, the model estimates the number of daily incidents in which UAE residents are exposed to mercury levels above the reference dose maintained by the U.S. Environmental Protection Agency due to eating fish. Results of daily cases in which a UAE resident may be at risk of overexposure to methylmercury from eating seafood and exceeding the reference dose suggest 2,927 women and 11,882 men—with the gender imbalance an artifact of the male-dominated expatriate workforce—could be at risk for health effects. Of all pesticides and crops, chlorpyrifos on tomato has the highest mean ratio (0.26) of average estimated pesticide exposure (0.000078 mg/kg) to its chronic population adjusted dose (cPAD) value (0.0003 mg/kg), making tomatoes the most suitable candidate for a worst-case hypothetical scenario. Considering an atypical but theoretical UAE resident eating 100% tomatoes, and assuming no reduction in pesticide due to washing, peeling, and/or cooking, the model estimates this person has 20.6% (chlorpyrifos) and 1.0% (vinclozolin) chances of exceeding cPAD values each day. Overall, this model estimates 631,074 worst-case daily incidents (cPAD exceedance) contributing to potential chronic illness. Although these probabilities may seem high, daily cPAD incidents are assumed contributory toward potential cases of annual chronic illness; the model assumes (worst-case) no reduction in pesticide due to washing, peeling, and/or cooking for all incidents; and, only very limited human epidemiologic studies exist to objectively link chronic pesticide exposure with adverse health effects—a major reason for the safety factors already built into the cPAD and other benchmarks.

The methods described in this book can provide a foundation for the next generation of environment and health strategic plans. Our approach provides an empirically validated means for the kinds of cooperative planning by the various levels of government, nongovernmental organizations and local communities needed in order to reduce human impacts on the environment and environmental impacts on human health. The project documented in this book followed three major steps: (1) developing preliminary environmental burden of disease estimates for 14 risk categories, (2) engaging stakeholders in a systematic process to prioritize these 14 risk categories based on the burden of disease information and other factors, and (3) analyzing in detail the burden of disease for eight key risk categories emerging from the priority-setting exercise. This chapter integrates the environmental burden of disease estimates from Chaps.​ 4, 5, 6, 7, 8, 9, 10, and 11. It provides a big-picture view of the United Arab Emirates’ environmental disease burden across risk categories. It then outlines how the environmental burden of disease model described in these chapters can serve as a foundation for systematically analyzing interventions to improve environmental quality and lessen the associated disease burden. Next, it explains how a process like that in Chap.​ 2 could provide the foundation for the next generation of environment and health strategic plans, in which stakeholders come together to prioritize environmental interventions from a menu of options. The chapter also explains how ecological impacts of interventions could be incorporated in this priority-setting process. The budget struggles that many nations face as they contend with the continuing global economic crisis underline the need for renewed environment and health strategic planning. The approach outlined in this book paves the way for doing more with less—for increasing the public health gains of environmental interventions without necessarily increasing the economic burden on governments and their citizens.