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Institute of Medicine (US) Roundtable on Environmental Health Sciences, Research, and Medicine; Merchant J, Coussens C, Gilbert D, editors. Rebuilding the Unity of Health and the Environment in Rural America: Workshop Summary. Washington (DC): National Academies Press (US); 2006.

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Rebuilding the Unity of Health and the Environment in Rural America: Workshop Summary.

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4The Built Environment and Health in Rural Areas*

Low population density, land use mix, and connectivity define urban sprawl, and urban sprawl is a major outcome of development strategies in the United States. Since the early 20th century, the population of the United States has shifted from living predominantly in rural areas to living predominantly in urban regions. The first year in U.S. history in which more people lived in cities than in rural areas was 1920 (U.S. Census Bureau, 2000a). Suburban growth was fueled by many factors, including the desire to avoid polluted cities. People considered suburban living to be healthier. Urban encroachment in rural areas creates health problems and issues involving health care access, air pollution, water pollution and water availability, and other concerns, said Bernard Goldstein of the University of Pittsburgh.


Specific health issues in rural areas need to be considered, said Goldstein. Access to health care, which can be difficult in rural areas, is such issue. For example, it is common for there to be only one main road going from a rural area into the nearest city with a hospital. Traffic congestion on that key road may impede ambulances from getting to the tertiary-care hospital. Also, the more rural the area, the more likely it is that people will die if they are in an automobile accident because people drive at higher speeds in rural areas.

Air pollution caused by automobile exhaust, traffic drive times, and stop-and-go traffic brings urban problems into rural areas. According to Goldstein, the areas with the worst ozone levels are usually not within the city but are immediately downwind of the city because ozone is formed relatively slowly by the action of sunlight on oxides of nitrogen and hydrocarbons.

Urban sprawl also creates water availability and water pollution issues. Suburban development has an impact on groundwater availability because in suburban areas water from rain and other precipitation is moved off the land and immediately enters rivers; thus, the groundwater does not get recharged appropriately. That is, the water rapidly enters the rivers instead of circulating through the ground until it eventually reaches the river. Also, water draining right off a parking lot may create storm water and sewage overflows.

Other problems in suburbia include the presence of optimal conditions for the transmission of Lyme disease and mosquito-borne disorders because of the interface between mosquitoes and humans.

Other health problems due to urban sprawl include heat islands, global climate change, noise, a lack of availability of healthy food choices, public health workforce issues, and safety issues such as crime and traffic. When a green area is replaced by asphalt, a bigger heat island results in changes in local temperatures and ecosystems. Heat island and temperature changes also affect the rural areas that are near the suburbs, noted Goldstein.

Attempts to try to understand the impact of urban sprawl on the public health workforce are beginning. The workforce is decreasing and the resources are diminishing at a time when the public health system is encountering some of its greatest challenges, said Goldstein. Furthermore, a large turnover of the public health workforce is anticipated because of retirement. The impact is different in different areas, but often the public health workforce in the rapidly growing suburban areas has less expertise because the budget for the public health infrastructure cannot keep up with the growth, noted Goldstein.

Is Europe the Answer?

Europeans have done an excellent job of keeping their cities and rural areas separate, said Goldstein. The Europeans protect their rural agricultural land and enforce their zoning laws rigidly, making it more difficult to build out from the existing areas of the community. European zoning laws encourage populations to be dense in urban areas by promoting the use of mass transit and the development of bikeways and walkways and by reducing the need for cars.

In Europe, political power and budgets are centralized. In almost every Western European country, its capital is also its largest and most powerful city. This is almost never true in U.S. states, as Americans culturally have less trust in the centralization of power, said Goldstein. The United States has a municipality or some governmental organization for every 3,500 citizens. Most of the local funding in the United States is derived locally, whereas most of the local funding in Western Europe, including funding for police, fire, rescue, and schools, is derived from the central government.

Americans have a frontier mentality, said Goldstein. Europeans do not move as frequently as Americans. The average American moves approximately seven times in his or her lifetime, whereas the average European moves less than two times. Between 1995 and 2000, 120 million (46 percent) Americans moved homes. Homes in the United States average 718 square feet per person, whereas in The Netherlands the average home size is 256 square feet per person.

The average American moves approximately seven times in his or her lifetime, whereas the average European moves less than two times. Homes in the United States average 718 square feet per person, whereas in The Netherlands the average home size is 256 square feet per person.

—Bernard Goldstein

It is overly simplistic to believe that the United States can or will follow the European example, concluded Goldstein.


Iowa has housing issues both in rural areas and in the inner cities of urban areas. One of the distinguishing features of Iowa’s housing, particularly compared with the housing features of its neighbors, is the age of its housing. According to the 2000 census, Iowa is fifth in the country in the percentage of houses built before 1950 and third in the percentage of houses built before 1940 (the District of Columbia is first and Massachusetts is second in the percentage of houses built before 1940). Although age is not the only factor that describes housing, it is a surrogate for many of the problems associated with housing, said Rita Gergely of the Iowa Department of Public Health. Rural counties in Iowa have the largest percentage—55 percent to 60 percent—of housing built before 1950 (Figure 4-1). Some of the houses that were built in the 1960s were not of good quality, and they have been abandoned and torn down, noted Gergely.

FIGURE 4-1. Percentage of housing built before 1950 in each Iowa county.


Percentage of housing built before 1950 in each Iowa county. Although age is not the only factor that describes housing, it is a surrogate for many of the problems associated with housing. SOURCE: U.S. Census Bureau (2000a).

According to a study of the Department of Urban and Regional Planning at the University of Iowa, dilapidated units are estimated to need more than $25,000 to $30,000 in repairs, but in some parts of the state, that amount might be more than the sale price of the house if those repairs were made (MacDonald, 2003). In rapidly growing areas, the proportion of units reported to be in poor and dilapidated condition ranges from 0.02 percent to 3 percent, whereas in the areas with declines in growth—which are largely rural areas—that proportion ranges from 3 percent to 9 percent (MacDonald, 2003).

Abandoned Housing

In general, abandoned housing is not an environmental health issue in Iowa, said Gergely. Rather, it is a nuisance that can impede economic development. However, housing is an issue in southern Iowa, where counties are trying to attract industry to the smaller towns. The executives who decide whether or not they are going to bring a company to a town base their decision on whether that town has decent places for their employees to live. If dilapidated housing is mixed in with better-quality housing, property values are lower.

Abandoned housing can become an environmental health and safety issue when, for instance, children play near houses that are in imminent danger of collapse. Abandoned buildings in remote rural areas are perfect places for methamphetamine labs, said Gergely. Also, people are often concerned that abandoned houses are a reservoir for rodents and insects that can travel to nearby homes, particularly in urban areas.

Iowa’s infrastructure has a very fragmented system for taking care of abandoned and nuisance houses. Iowa Code 657A defines an abandoned house as one that has been vacant and in violation of the city or the county housing code for at least 6 months. If a house can be defined as an abandoned house, a neighbor or a nonprofit housing organization can petition the court to order the property owner to make repairs. If the property owner is not willing to make the repairs or cannot afford it, the court can appoint a receiver to make the repairs.

The cities and counties in Iowa have some additional powers to take care of abandoned homes. Iowa Code 331.384 provides for special assessments for the abatement of public health and safety hazards. A county can require the abatement of a nuisance in any reasonable manner; it may require the repair, removal, or dismantling of an abandoned or dangerous building or structure. Chapter 364 of Iowa Code 331 states that a city can condemn a residential building that is found to be a public nuisance and that the city can take title to the property so that it can dispose of it by conveying it to a private individual to rehabilitate or demolish and construct new housing.

Environmental health issues in the context of occupied housing include lead poisoning in children, carbon monoxide, fire and electrical hazards, water damage and mold, private wastewater treatment systems, the lack of rental housing codes, and improper sanitary conditions.

—Rita Gergely

Occupied Housing

Environmental health issues in the context of occupied housing include lead poisoning in children, carbon monoxide, fire and electrical hazards, water damage and mold, private wastewater treatment systems, the lack of rental housing codes, and improper sanitary conditions. Water damage and mold in homes result from flooding, leaking roofs and windows, plumbing problems, excess humidity in bathrooms and kitchens, and wet basements. These are more likely to be found in older and poorly maintained homes, noted Gergely, and can cause health problems in susceptible people. The awareness that these conditions can lead to the growth of mold, which can be a significant environmental health issue, is increasing.

In Iowa, only communities with populations of at least 15,000 are required to have rental housing regulations. Communities of this size have 173,186 units of rental housing built before 1950, which represents about 36 percent of Iowa’s rental housing stock built before 1950. According to Gergely, the housing code options listed in the Iowa Code are obsolete. No state agency has the authority to ensure that the cities that are required to have rental housing codes actually have them and are enforcing them, said Gergely. If a community has no rental housing code, the only option for a tenant dissatisfied with the condition of a house is to move or to bring civil action under the Iowa Landlord Tenant Act.

Lead poisoning is essentially a housing issue, said Gergely. Lead poisoning among children is a statewide issue in Iowa. When lead poisoning tests were performed for 55 percent of the children statewide, 9.4 percent of the children tested were found to have lead poisoning. According to the National Health and Nutrition Examination Survey (NHANES), the current national average rate of lead poisoning among children is 2.2 percent (CDC, 2003). Lucas and Wayne Counties have the highest prevalence of lead poisoning in the state. These two counties have high poverty rates, and almost half of all houses in the counties are more than 50 years old.

Another issue in Iowa is carbon monoxide. If appliances that are fueled with gas, oil, kerosene, or wood are not installed, maintained, and used properly, they are bound to cause death from carbon monoxide poisoning. More recent evidence also indicates that carbon monoxide poisoning can cause some long-term sudden neurological effects, even if those who are exposed do not die. Moreover, attempts to tighten up houses to make them more energy efficient can lead to indoor air quality issues, including high levels of carbon monoxide.

Outdated and improperly maintained electrical wiring of furnaces, water heaters, dryers, and other appliances can cause fires in older homes. Additionally, inadequate wiring in older homes leads to the more extensive use of extension cords and power strips, which, if improperly used, can cause fires.

It is estimated that 4.5 billion gallons of untreated or improperly treated human waste is being discharged from the 400 to 600 small rural communities (existing areas and new subdivisions) in Iowa that do not have appropriate waste-water treatment facilities. These numbers do not include private systems outside communities or subdivisions. An estimated 80 percent of these existing systems are not property constructed and are causing problems. There is little evidence that improper private wastewater treatment systems are actually making people sick. However, if sewage is being discharged to the surface, it may cause illness in children and pets playing in it, noted Gergely.

The Iowa Department of Public Health receives many complaints about people living in extremely unsanitary conditions, such as in the presence of extreme clutter; with no running water or indoor plumbing; and with large numbers of pets, which could be reservoirs for diseases carried by rodents or insects. Unfortunately, government cannot do anything about a lack of running water or indoor plumbing if the property is owner-occupied unless there is a violation of city codes or zoning regulations, the conditions are endangering the health of a child or an elderly person who has no choice in the matter, or animals are being neglected.

Because housing quality is a problem in so many communities, it is difficult to determine priorities for action, and the rural areas are always the ones to lose out when funds are cut, concluded Gergely.


As in the rest of the United States, obesity is a growing health concern in Iowa. The state has the 17th highest rate of adult obesity in the nation (23.9 percent) and the 10th highest rate of overweight among low-income children ages 2 to 5 years (13.6 percent) (Trust for America’s Health, 2005). In 2003, the state spent an estimated $266 per person on medical costs related to obesity, which was the 21st largest amount in the nation (Trust for America’s Health, 2005). Most Americans are eating too much for a variety of reasons. One of the reasons is that many people do not understand exactly what they are eating because the community does not understand many of the healthy diets that are being promoted, said John Lowe of the University of Iowa. People living in the United States consume a lot of inexpensive, high-calorie, dense food with large portion sizes, and at the same time they are less physically active, noted Lowe. If energy intake is greater than energy expenditure, one gains weight. The large numbers of eating establishments and other social institutions, such as fast-food outlets, convenience and grocery stores, bars and liquor stores, parks, and recreational facilities, influence caloric consumption and activity levels. Opportunities for the infrastructure to be used to help people participate in physical activity are not present at proportional densities, noted Lowe.

There are different types of physical activity: (1) programmed physical activity and exercise; (2) occupational physical activity, which is decreasing in rural areas; (3) lifestyle physical activity, which is when, for example, people take the stairs instead of an elevator; and (4) transportation physical activity, such as walking or bicycling. The physical environment, such as residential areas, the grounds, and sidewalks, has a direct impact on obesity because the physical environment either encourages or discourages people to exercise, noted Lowe. Unfortunately, the sidewalks in most counties in Iowa are deteriorating, and there is no funding within the communities to fix them. The grass continues to overgrow, which makes it difficult for the aged population to walk; thus, injuries related to physical activity are a concern. Socioeconomic factors, such as personal or household income, material deprivation, unemployment, a lifetime history of poverty, asset ownership, and the receipt of welfare, affect one’s physical activity as well, said Lowe.

There are different types of physical activity: programmed physical activity and exercise; occupational physical activity, which is decreasing in rural areas; lifestyle physical activity, which is when, for example, people take the stairs instead of an elevator; and transportation physical activity, such as walking and bicycling.

—John Lowe

To address some of the issues mentioned above, the University of Iowa’s College of Public Health established a partnership in Keokuk County called Community Health Action Partnership (CHAP). The partnership is community driven, with 18 organizations and about 40 members currently involved. The community chooses the topics and the university provides expert consultation to help facilitate activities and make sure that what they do is evidence based. The community group identified three areas in which it wanted to work: physical activity, nutrition, and adolescent alcohol use. As a result of the partnership’s activity, Keokuk County is the first county in Iowa to have passed a beer keg registration ordinance, which requires people who get a beer keg to register it in their name. Therefore, when the keg is found it can be traced back to the individual who purchased it. On the basis of some of the proximal data, alcohol consumption by youths appears to be going down, said Lowe, and the partnership wants to take the same initiative statewide.

The nutrition group of CHAP is chaired by the owner of the local supermarket. Pepsi and Coca-Cola have seats on the county’s CHAP group as well. (Both of these businesses have seats on CHAP because they are willing to explore less harmful ways of making profits for their stockholders.) The university works with the local supermarket, and the university’s data helped the supermarket revisit the selection of goods on its shelves. The result was the promotion of water and reductions of Pepsi and Coca-Cola beverage choices, said Lowe. The partnership worked with the school district and superintendent, and it is now permissible to take water into class, which encourages schoolchildren to purchase and drink water.

Furthermore, the community proposed that a walking trail be built, and the proposal became an issue of discussion. Some people were opposed to it because they did not want the trail to go through their backyards but the positive outcome of the discussion was that physical activity became the topic of conversation. It increased the proportion of people who talked and thought about physical activity. The trail is under construction, and the community is very proud of it. However, issues of safety and lighting on the trail remain, because it may not be safe to walk on the trail after dark.

There are no data to support the concept “if you build it, they will come,” said Lowe. Community acceptance of the idea of exercising is key to getting families to use the walking trail.

The idea of increasing physical activity and decreasing consumption is going to take a social, cultural, and physical environmental change, concluded Lowe. It is not enough for health professionals to tell people to eat less and to go out and exercise more. The community, along with work sites and faith institutions, will have to get involved in promoting healthier lifestyles and will play a key role in changing the social acceptance of and social environment for physical activity.


In general, farmers are healthier, live longer, smoke less, and are more physically active than the general population, although they are still at higher risk for some diseases compared with the risk for the general population, said Jane Hoppin of the National Institute of Environmental Health Sciences. Respiratory morbidity, hearing loss, suicide, and neurological diseases such as Parkinson’s disease are more common among farmers. The rates of specific cancers, including prostate cancer, lip cancer (which is associated with sunlight exposure), and lymphomas are increased among farmers. Other widely spread morbidities and causes of mortality among farmers are adverse reproductive outcomes and accidents.

In general, farmers are healthier, live longer, smoke less, and are more physically active than the general population, although they are still at higher risk for some diseases compared with the risk for the general population.

—Jane Hoppin

Farmers grow up and spend most of their lives on a farm, where they are exposed to pesticides, both organic and inorganic fertilizers, dust, grains, animals, diesel exhausts, and solvents, said Hoppin. They live where they work and may carry home their occupational exposures. According to Hoppin, pesticide exposures on farms are infrequent compared with the frequencies of exposures to other products. The lengths of pesticide applications range from 1 day to more than 100 days per year, and the pattern of pesticide use is influenced by the crop planted, including genetically modified crops; the weather conditions; the region; and the calendar year. Pesticide products contain other ingredients, such as silica and solvents, which are often present at much higher concentrations than the pesticides themselves and may influence the toxic exposure to pesticides.

The Agricultural Health Study

The Agricultural Health Study (AHS) was designed to study a wide range of health effects of agricultural exposures in farmers and their families. It is a collaborative venture between the National Cancer Institute, the National Institute of Environmental Health Sciences, the U.S. Environmental Protection Agency, and the National Institute of Occupational Safety and Health (National Institute of Environmental Health Sciences, National Cancer Institute, U.S. Environmental Protection Agency, 1993). The exposures studied by AHS include those to pesticides, animals, diesel, and solvents. The health effects considered by the study include cancer, respiratory health, reproductive outcomes, and neurological disease. The study population is a prospective cohort of farmers and their spouses in Iowa and North Carolina. Having the two states in the study provides diversity, because Iowa’s agricultural methods are very homogeneous, whereas North Carolina’s agricultural methods are very diverse; in North Carolina, even tobacco-growing methods in the mountains are different from those in the coastal regions, noted Hoppin. Furthermore, the study included only farmers and their spouses and not farmworkers because the study was designed to monitor individuals over time, and long-term studies of farmworkers were outside the scope of the study.

People who obtained their pesticide license between 1993 and 1997 were enrolled in the study by completing a questionnaire, which gathered information not only on their pesticide use, but also on their smoking and disease histories. Exposure-related information was gathered from the farmers and their spouses and included information on the agricultural application of pesticides; the crops and animals that they raised; their various farming activities, including whether they drove a diesel tractor or used natural as well as chemical fertilizers; where they get their drinking water; and aspects of home hygiene, such as whether they wear work boots in the house and whether clothing worn while working in the field is mixed with the family laundry. Approximately 84 percent of the people who were licensed private pesticide applicators in the two states between 1993 and 1997 enrolled in the study, and 75 percent of the married applicators had their spouses enroll. The researchers reinterview the farmers every 5 years—regardless of whether they are currently farming and whether they are currently married to each other—and the cohort is linked annually to the National Death Index and each state’s Cancer Registry. Validation of exposure is estimated through field monitoring.

Study Participants’ Characteristics

The study cohort contained 52,000 private pesticide applicators and 32,000 spouses, and two-thirds of the cohort lived in Iowa. The study participants were predominantly white, because African American farmers have left farming at a more rapid rate than white farmers, noted Hoppin. There were more male applicators and more female spouses in the cohort, and slightly less than half of the participants were more than 50 years old when they enrolled in the study. The individuals ranged from 18 to 88 years of age, and the majority of them had more than a high school education.

AHS Mortality, 1993–2000

Since the beginning of the study in 1993, there have been approximately 1,500 deaths among the participants in the cohort. The death rate is half of what is expected on the basis of a 0.5 standardized mortality ratio (SMR), which compares the rates of mortality of the pesticide applicators and their spouses with those of other people living in Iowa of the same race, sex, and age (Table 4-1). The rates of death from all causes, with the exception of non–motor vehicle accidents, are lower among the pesticide applicators. The rates of cardiovascular disease and chronic obstructive pulmonary disease among the pesticide applicators are considerably lower than those among the general population, and it is likely that this is due to their high rates of physical activity and low rates of smoking.

TABLE 4-1. Mortality Rates from Agricultural Health Study, 1993–2000.


Mortality Rates from Agricultural Health Study, 1993–2000.

AHS Cancer Incidence

Compared with the general population, the AHS cohort had no elevated risks of cancer. Similar to the general population, the most common cancer among the men in the cohort was prostate cancer, and the most common cancer among the women in the cohort was breast cancer. By comparison of the chemical exposures among individuals within the cohort, only 1 of more than 40 chemicals tested—a common soil fumigant, methyl bromide—was associated with prostate cancer. Additionally, there was a slight association between the application of chlorinated pesticides and prostate cancer. However, older people, who are more likely to get prostate cancer, were also more likely to have applied chlorinated pesticides, said Hoppin. Because prostate cancer is such a common cancer, the study needs to be repeated in 2 or 4 years to conduct a new analysis to see if the previous results are replicated.

According to the findings of the study, the overall breast cancer rates in the cohort are not elevated compared with the rate in the general population. However, when the cohort spouses were separated out by women who reported pesticide use and women who did not, women who reported that they applied pesticides had much lower rates of breast cancer than women who did not. This could be because women who are doing farmwork are more physically active, but more studies are needed to understand this finding, said Hoppin.

Compared with the rates in the general population, both the overall rates of lung cancer and the smoking rates were lower in the cohort. However, the study showed that some individual chemicals, such as the herbicides metolachlor and pendimethalin and the insecticides chlorpyrifos and diazinon, may be associated with lung cancer risk. Whether this association is due to the chemicals themselves or silica, which may be an inert ingredient in some of the chemicals, will require further investigation, said Hoppin. Some participants noted that in general there is no variety of lung cancer that is more common to farmers. According to Hoppin, researchers do not yet have enough lung cancer incidences to break them out into various subtypes. It is possible that in four years researchers will be able to determine whether there are different lung cancer types that are more common among farmers.

AHS Findings on Neurological Effects

The findings on neurological effects are based on cross-sectional data from information that the study participants reported in the questionnaire when they enrolled in the study, noted Hoppin. Recently, the second phase of the study was completed, and the follow-up data will allow prospective examination of the exposures.

Pesticides are designed to interfere with the neurological systems of insects; therefore, it is expected that they would have neurological effects in humans as well. In general, exposure to high levels of insecticides, particularly the organophosphates, can cause a disease called organophosphate-induced peripheral neuropathy, which is a long-term consequence of exposure to a very high dosage. However, little is known about chronic, moderate, or low-level exposures. Approximately 19,000 male private pesticide applicators were studied for neurological effects. The study evaluated 19 symptoms as a whole, including headache, fatigue, tension, insomnia, irritability, dizziness, numbness, depression, vision, sweating, tremor, nausea, and balance. By considering these symptoms as a whole, the researchers were able to look at the various constructs of the central nervous system and see how people might be affected by these vague symptoms and if they are associated with application of a particular type of pesticide. The study found that chronic neurological symptoms were associated with the lifetime use of insecticides and fumigants. The strongest associations were with organochlorines and organophosphate insecticides and a history of pesticide poisoning. Furthermore, insecticides in general were associated with all aspects of neurological function, including affect and cognition functions, systemic and peripheral nervous system functions, and motor and vision functions.

Retinal degeneration is a leading cause of visual impairment in older adults. It is more common among white women; people with light eye color, cardiovascular disease, or hypertension; and people with a family history of the condition, noted Hoppin. The risk factors for this condition are not known, and there is no occupational exposure literature suggesting that occupational exposures could be associated with retinal degeneration. However, there is also no literature that says that retinal degeneration is not associated with occupational exposures, said Hoppin. In experiments with animals, there is evidence of a possible risk of retinal degeneration from organophosphate insecticides. In the AHS cohort, individuals with retinal degeneration were more likely to report the use of fungicides and the production of orchard fruit (Kamel et al., 2000). The odds ratio for fungicide use among the farmers with retinal degeneration was 1.8, which suggests an 80 percent increase in retinal degeneration among people who reported that they used fungicides. In a more recent analysis among the farm women, an odds ratio of 1.9 was observed for women who reported using fungicides and having retinal degeneration (Kirrane et al., 2004).

Farmers and Respiratory Disease

Respiratory disease among farmers is one of the first occupational diseases described in the literature dating back to the 1500s. The exposures on farms have changed since then, but the disease continues among farmers, said Hoppin. Farmers have some common respiratory health outcomes, such as asthma, declines in pulmonary function, and increased bronchial hyperresponsiveness. Also, farmers get a unique disease called farmer’s lung, which is primarily related to handling moldy hay and grain and is associated with living in more northerly latitudes. One of the strengths of the AHS is that it has the power to assess the wide array of possible respiratory toxicants in the same group of individuals. At enrollment, the participants were asked about the occurrence of asthma, bronchitis, emphysema, farmer’s lung, hay fever, and the common respiratory symptom wheeze (wheeze is the whistling sound made while breathing; it is associated with bronchial constriction or chest tightness and is the cardinal symptom of asthma).

The cross-sectional data on the rates of these symptoms show that the rate of asthma seems to be lower among the farmers than among those in the general population; the rates of bronchitis and emphysema are similar; the rate of farmer’s lung in the general population is not researched because of its low prevalence; and hay fever is slightly more common in the farmers than it is in the general population, particularly when the data for the farmers are compared with the NHANES data for the U.S. population (Table 4-2). The rate of the respiratory symptom wheeze is striking among farmers: 19 percent of the applicators reported wheeze, whereas only 13 percent of the general population reported the same symptom. Three different types of exposures—pesticides, animals, and other farm exposures—were evaluated as causes of wheeze. Eleven of 40 pesticides were positively associated with wheeze, and the dose trends for 10 of those were significant. Three organophosphates—parathion, malathion, and chlorpyrifos—were associated with wheeze. The highest odds ratio (1.5) was observed for parathion, which is one of the most potent organophosphates (Hoppin et al., 2002). The study revealed that the risk of wheeze increased with the overall number of days of pesticide, insecticide, and herbicide use. No trend with the number of days of total use of any organophosphates or carbamates was observed, which suggests a role for individual chemicals.

TABLE 4-2. Rates of Respiratory Outcomes Among Participants in the AHS at Enrollment (percent).


Rates of Respiratory Outcomes Among Participants in the AHS at Enrollment (percent).

Animal exposures are associated with wheeze as well. People who have contact with animals, who work with dairy cattle or poultry and eggs, or who perform veterinary procedures are more likely to report wheeze. People who raise hogs, however, had almost no evidence of wheeze.

Other agricultural exposures associated with increased rates of respiratory symptoms, particularly wheeze, were exposure to manure as a natural fertilizer, exposure to diesel while driving diesel-fueled tractors (people who drove gasoline-fueled tractors did not have the same symptoms), and exposure to solvents for cleaning.

The AHS will continue with its next round of interviews and plans to analyze data on specific chemicals and cancer, Parkinson’s disease, respiratory disease, rheumatoid arthritis, and the overall rate of mortality among the members of the cohort over time, concluded Hoppin.

The views expressed here do not necessarily reflect the views of the Institute of Medicine, the Roundtable, or its sponsors. This chapter was prepared by staff from the transcript of the meeting. The discussions were edited and organized around major themes to provide a more readable summary and to eliminate duplication of topics.



The views expressed here do not necessarily reflect the views of the Institute of Medicine, the Roundtable, or its sponsors. This chapter was prepared by staff from the transcript of the meeting. The discussions were edited and organized around major themes to provide a more readable summary and to eliminate duplication of topics.

Copyright © 2006, National Academy of Sciences.
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