Agricultural task and exposure to organophosphate pesticides among farmworkers.

Little is known about pesticide exposure among farmworkers, and even less is known about the exposure associated with performing specific farm tasks. Using a random sample of 213 farmworkers in 24 communities and labor camps in eastern Washington State, we examined the association between occupational task and organophosphate (OP) pesticide residues in dust and OP metabolite concentrations in urine samples of adult farmworkers and their children. The data are from a larger study that sought to test a culturally appropriate intervention to break the take-home pathway of pesticide exposure. Commonly reported farm tasks were harvesting or picking (79.2%), thinning (64.2%), loading plants or produce (42.2%), planting or transplanting (37.6%), and pruning (37.2%). Mixing, loading, or applying pesticide formulations was reported by 20% of our sample. Workers who thinned were more likely than those who did not to have detectable levels of azinphos-methyl in their house dust (92.1% vs. 72.7%; p = 0.001) and vehicle dust (92.6% vs. 76.5%; p = 0.002). Thinning was associated with higher urinary pesticide metabolite concentrations in children (91.9% detectable vs. 81.3%; p = 0.02) but not in adults. Contrary to expectation, workers who reported mixing, loading, or applying pesticide formulations had lower detectable levels of pesticide residues in their house or vehicle dust, compared with those who did not perform these job tasks, though the differences were not significant. Future research should evaluate workplace protective practices of fieldworkers and the adequacy of reentry intervals for pesticides used during thinning. Key words: applicators, farmworker, field worker, job task, occupational exposure, pesticide.

**********

Farmworkers in various aspects of U.S. agriculture are routinely exposed to pesticides as part of their occupation. Many of these workers perform job tasks that have high risk for direct exposure to pesticides, such as mixing, loading, or applying pesticide formulations. The U.S. Environmental Protection Agency's Worker Protection Standards (U.S. EPA 1992) mandates that personal protective equipment and training be provided to these workers. Workers with direct pesticide contact are required to carry a pesticide handlers' permit or a pesticide license and, therefore, are required to receive training in the proper use and storage of pesticides and in protective measures to minimize exposure. The patterns of pesticide exposure and the effectiveness of protective measures among this group have been the topics of previous research (Alavanja et al. 1999a, 1999b; Arbuckle et al. 2002; Dosemeci et al. 2002; Garry et al. 2002a, 2002b; Gladen et al. 1998; Hoppin et al. 2002; Karr et al. 1992; Loewenherz et al. 1997; O'Fallon and Dearry 2001) and policy recommendations (cholinesterase monitoring) in recent years (Wilson et al. 1997).

The pattern of exposure is less understood among workers who perform tasks that do not require the use of personal protective equipment or safety training, such as harvesting crops, pruning vines and trees, loading or packing plants fruits and vegetables, or thinning orchards. Some of these workers may have substantial physical contact with fruits, leaves, twigs, and branches that may contain pesticide residues. Because many fieldworkers work on several crops, they may be exposed to several different types of pesticides throughout a given growing season. A limited number of previous investigations have examined workplace protective practices of this group (such as the frequency of use of gloves, long-sleeve shirts, and long pants) (Jackson 2002; Vela-Acosta et al. 2002); only a limited number have assessed pesticide exposure among this group (Fenske et al. 1999; McCurdy et al. 1994; Simcox et al. 1999).

Even less is known about the patterns of exposure of children living in households with farmworkers. A limited number of previous investigations have suggested that the children of farmworkers may experience adverse effects of pesticide exposure. Two studies that examined cancer end points among children of farmworkers reported elevated incidence of leukemia (Daniels et al. 1997) and cancers of the brain (Daniels et al. 1997) and kidney (Fear et al. 1998). A related study found miscarriage and fetal loss to be more common among spouses of pesticide applicators than among spouses of nonagricultural workers. Moreover, miscarriage and fetal loss were more commonly experienced during the spray season (Garry et al. 2002a, 2002b).

It is widely believed that pesticide residues in the home environment are exposed to little sunlight or water and thus break down at a slower pace than pesticides in fields and orchards. Children may be uniquely susceptible to this exposure because they spend greater amounts of time on carpets and floors (where pesticides accumulate), they often wear minimal clothing during the summer spray season (increasing their likelihood of dermal exposure), and they engage in hand-to-mouth behavior (increasing their likelihood of ingesting pesticides) (Mills and Zahm 2001). With less developed immune systems than adults, children may be less able to clear pesticides from their bodies, thus prolonging the effects of exposure (Mills and Zahm 2001).

Using a quasi-population-based sampling technique and a large sample of farmworkers from several agricultural communities in eastern Washington State, we sought to examine the association between specific agricultural tasks and levels of pesticide exposure among adult workers and children living in the same household. We used adult and child urinary pesticide metabolite concentrations and dust residues from vehicles and cars of the same set of households as markers of exposure. In this report, we use the term farmworker generally to mean any agricultural worker, including seasonal workers and growers.

Methods

Setting. This study is part of a larger study that sought to develop and test a culturally appropriate intervention to break the take-home pathway of pesticide exposure. The setting, study design, study participants, and survey procedures have been described previously resistant organisms, including nonenveloped viruses and bacterial spores. Because all federal and state requirements are based on less-resistant indicator organisms, it is not known whether current methods, including aerobic and anaerobic digestion, heat treatment, lime stabilization, and composting, could achieve high-level disinfection.

Pathogen Regrowth

Although high-level disinfection would afford greater protection for both workers and the public from pathogens in freshly processed sewage sludge, the public can also be exposed to pathogens that proliferate after the sludge is applied (Gibbs et al. 1997). Viruses do not replicate outside their hosts; therefore, pathogen regrowth is mainly of concern with bacteria and fungi. Consequently, while viruses and other pathogens die off in the field, some pathogens may rebound. Also, new pathogens are introduced when sludge is mixed with soil and comes in contact with insects, birds, mammals, and other environmental sources of pathogens.

The potential for pathogen regrowth is the downside to sewage sludge being rich in nutrients that promote the growth of bacteria and fungi. The problem is similar to food poisoning with perishable foods, such as egg products. Eggs, like raw sewage, are often contaminated with Salmonella. With a little cooking, however, egg-containing products are safe for human consumption. Nevertheless, unless these foods are desiccated or refrigerated, other pathogens, such as S. aureus, multiply in them. The source of S. aureus in spoiled food is not the eggs, however, but normal skin microflora from the hands of people who prepare or handle the food.

Although sewage sludge is not a food product, the principle is the same. Sludge is rich in proteins and other nitrogen-rich organic compounds that promote the growth of S. aureus and other bacteria. These organisms multiply as sludges decompose in soil, and can present a risk of infection when traces of sludge enter skin abrasions or when the dusts contact mucous membranes or are inhaled. The risk is particularly high when sewage sludge contacts tissues injured by chemical irritants, burns, cuts, or abrasions. People with chronic diseases and compromised immune systems are especially at risk.

Also, as is the case with food products, sewage sludge that is heated or otherwise treated to kill pathogens is still subject to pathogen regrowth. In fact, because most of the competing microorganisms are eliminated, it is even more conducive to pathogen regrowth. Leaving pathogens in sewage sludge, however, is not the solution.

Unfortunately, pathogen regrowth is an inherent problem with all sludges rich in proteins, amino acids, and other forms of organic nitrogen and sulfur--regardless of how they are processed. Once the materials are applied and become wet, they are colonized by bacteria and fungi; the materials then decompose and emit noxious odors in the form of organic amines, organic sulfides, and other small-molecular-weight compounds.

Offensive odors that form as sludge biologically decomposes in the field indicate pathogen regrowth because they are produced as bacteria break down proteins and other organic compounds containing nitrogen and sulfur. Most treatment methods produce sludges that are only temporarily stable; that is, the sludges produce noxious odors from biological decomposition after they are applied in the field.

One commercial process achieves long-term stability by chemically reacting sludge under heat and pressure at high pH to drive off organic nitrogen as ammonia (Reimers et al. 2003). With this process, the combination of gaseous ammonia, high temperature, and pressure effectively eliminates a wide range of pathogens. The final wet product, which is odorless and has a high pH, is used to amend acidic soils. Because the nitrogen content is driven off, however, the product lacks nutrient value.

Bacterial Toxins

Most bacteria found in sewage sludge produce either endotoxins or exotoxins, both of which can cause severe illness or death. As sludges decompose, toxins can leach into groundwater, enter surface water runoff, and be carried away in airborne dusts. Considering that tons of decomposing sewage sludge per acre are often applied to hundreds or thousands of acres many times a year, land-application sites have a potential for producing and exporting large quantities of toxins.

Exotoxins--proteins and peptides secreted into the surrounding environment by growing cells--are produced by both gram-negative and gram-positive bacteria. They are usually the most toxic of the two general types of bacterial toxins. Because they can retain their toxicity at extremely high dilutions, some exotoxins, including staphylococcal enterotoxins and shigatoxin, are used as biological warfare agents.

Although exotoxins are generally heat labile and could therefore be destroyed by heat-treatment processes for sewage sludges, treated sludges are still likely to become contaminated with E. coli, Pseudomonas auruginosa, and other exotoxin-producing bacteria in the field. Severe gastrointestinal illnesses reported by individuals using private wells near land-application sites may have been caused by exotoxins leaching into groundwater.

The same property that makes S. aureus a common cause of food poisoning--its ubiquitous presence--may also make it one of the more common pathogens to proliferate in sewage sludges after they are applied to land. The organism produces an exotoxin that is not destroyed by cooking. Symptoms caused by S. aureus food poisoning (e.g., nausea, cramps, vomiting) are due to the presence of this toxin. Land-application sites with high levels of S. aureus could contaminate air and water with potentially harmful levels of both the organism and its toxin.

Endotoxins, on the other hand, are lipopolysaccharide complexes in the cell walls of gram-negative bacteria only. They are associated with proteins and other components of the cell walls and are released when the bacteria die and cell walls break apart (Rylander 1995). Endotoxins are produced in large quantities when wastes colonized with gram-negative bacteria are treated (Sigsgaard et al. 1994). They would also be produced as gram-negative bacteria growing in nutrient-rich sludges die off in the field.

Unlike most exotoxins, endotoxins are heat stable even upon autoclaving (Baines 2000). They can, however, be inactivated with dry heat at > 200[degrees]C for 1 hr (Williams 2001). Traces of endotoxins in food and water can cause headaches, fever, fatigue, and severe gastrointestinal symptoms; however, their primary target is the lungs. In addition to the former symptoms, inhaling endotoxin-contaminated dusts can cause acute airflow obstruction, shock, and even death. Chronic respiratory effects can also develop [American Conference of Government Industrial Hygienists (ACGIH) 1999].

Allergic and nonallergic reactions caused by airborne endotoxins have been documented with exposures of 45-150 endotoxin units (EU)/[m.sup.3] and 300-400 EU/[m.sup.3] (Milton et al. 1996; Smid et al. 1994). Nearby residents exposed to dusts from land-application sites report many of the same symptoms of endotoxin poisoning that have been documented among sewage treatment plant workers. These include flu-like symptoms, nausea, vomiting, diarrhea, headaches, and difficulty breathing (Lewis et al. 2002). Rylander (1987) proposed occupational exposure limits to endotoxin-contaminated cotton dusts. Based on average air concentrations over an 8- to 10-hr workday, he suggested limits ranging from 200 EU/[m.sup.3] to prevent airway inflammation to 20,000 EU/[m.sup.3] to avoid toxic pneumonitis. The exposure levels of endotoxin-contaminated aerosols with sewage treatment plant workers have ranged from 80 to 4,100 EU/[m.sup.3] (Liesvuori et al. 1994). The toxins, however, have a greater effect on people with immune systems compromised by injury or illness (Barnes 2000).

Chemical-Pathogen Interactions

Although many chemical contaminants found in processed sewage sludges may potentially interact with pathogens to cause, facilitate, or exacerbate the disease process through allegeric and nonallergic mechanisms, microbial byproducts formed during the processing and decomposition of sewage sludge probably account for most of the acute health effects. Complaints among residents living near land-application sites are primarily respiratory related and are consistent with hypersensitivity reactions, including fever, cough, difficulty in breathing, nausea, and vomiting.

Numerous diseases involving immunologically mediated hypersensitivity reactions have been documented among workers exposed to organic dusts containing microbial products. Yi (2002) listed 27 diseases, each categorized according to the source of the dusts and the specific microorganisms identified as the primary cause of hypersensitivity. Sources include, for example, dusts from molded hay, mushroom compost contaminated with fungi and actinomycetes, Streptomyces-contaminated fertilizers, Caphaloporium-contaminated sewage, and wood contaminated with Bacillus subtilis.

Byssinosis, perhaps the most studied of these diseases, is attributed to traces of endotoxins from the breakdown of E. coli and other gram-negative bacteria on raw cotton fibers. Similarly, illnesses have been documented among wastewater treatment plant workers exposed to endotoxins in aerosols (Rylander 1987). Usually, the disease affects only a small percentage of sensitive workers.

Compared with waste treatment plant aerosols, however, endotoxin levels are probably much higher in sewage sludge dusts, which contain large numbers of predominantly gram-negative bacteria killed during treatment processes and after land application. Consequently, the frequency and severity of hypersensitivity among groups exposed to sewage sludge dusts may be much greater compared with exposure to other organic dusts.

Respiratory-related hypersensitivity is generally reversible when affected individuals are removed from the source of exposure and treated with high doses of corticosteroids. Corticosteroids used to treat the underlying inflammation, however, seriously impair the immune system. In the case of sewage sludge, this would render hypersensitive individuals highly susceptible to infection from the low levels of viruses, bacteria, fungi, and other pathogens in processed sludges.

Treating residents near land-application sites who experience hypersensitivity to processed sewage sludges, therefore, is both costly and risky. It would involve relocating affected individuals to another area, making certain that any potentially serious infections have been eliminated or controlled with antibiotics, then administering high doses of corticosteroids and closely monitoring for any new infections.

Exposure Studies

A conference on health effects of odors sponsored by Duke University and the U.S. EPA concluded that gases and volatile emissions from waste products including processed sewage sludge may cause adverse health effects (Schiffman et al. 2000). While acknowledging the complexity of the problem, the participants recommended undertaking controlled studies of the odorous emissions. In responding to the NRC recommendations (NRC 2002), the U.S. EPA committed to measuring field concentrations of selected volatile and gaseous compounds at selected sites (U.S. EPA 2003a).

Land-applied sewage sludge can emit numerous volatile chemicals and gases that may act alone or in combination with one another to produce the kinds of symptoms reported by people living near biosolids-recycling operations. The composition of air contaminants emitted by any land-application site undoubtedly varies widely over space and time, as do the susceptibilities of individuals to the effects of these emissions. Consequently, it is unlikely that such research will adequately establish which components and combinations of components can potentially cause adverse health effects and under what conditions.

We propose an alternative approach with a more modest goal aimed at determining the extent to which emissions must be diluted to eliminate malodor complaints and irritant effects (e.g., burning eyes, coughing, breathing difficulties). Based on meteorologic data from local weather stations and publicly available topographic data, the dilution of air contaminants over areas surrounding land-application sites can be readily determined with an air-dispersion model (Lewis et al. 2002).

Meteorologic data should be collected over an extended period of time (e.g., 6-8 weeks) during the maximum potential exposure, for example, when land application is in progress, temperatures are high, and sufficient rainfall has occurred to support high levels of microbial activity. This approach does nor require measuring specific pollutants, and a number of laird-application sites could be studied with a reasonable level of resources.

In addition to collecting meteorologic data, local census data would be used in this type of study to randomly select two groups of residents of similar demographic compositions: one close to the land-application site (< 1 km) and one farther away (3-5 km). Individuals in each group would provide information on medical histories and keep daily records of the selected symptoms during the period when meteorologic data are collected. Using a similar approach, we found that residents living closer to land-application sites were more severely affected than those living farther away (Lewis et al. 2002).

Quantitatively, what is needed is a simple numerical index that captures the most important variables determining whether symptoms develop. The amount by which volatile emissions are diluted when they reach a residence and the number of times the dilution drops below a certain level may be sufficient for predicting whether odor and health-related complaints are likely to develop.

For example, an exposure index could be calculated based on a) the number of exposures in which levels of volatile chemicals at a residence are [greater than or equal] 10% of the levels over the sludged field and b) the average percent dilution for these exposures. This approach is illustrated by Equation 1, where Iv is the exposure index for volatile emissions, n is the number of exposures in which levels of gases and volatile chemicals at a residence were [greater than or equal] 10% of the levels over the sludged field, and d is the average dilution (percent) for all exposures [greater than or equal] 10% of the levels over the field.

[1] [I.sub.v] = n * [??]]

Once exposure indices and frequencies of symptoms are collected for a number of land-application sites, a representative dilution level required to eliminate odor complaints and acute adverse health effects can be determined. This index provides a quantitative measure of whether a land-application site is likely to cause odor complaints and acute adverse health effects at a particular location or distance from the site. Such information could be used to evaluate the effectiveness of treatment methods and land management practices.

Public Concerns

To assess public concerns over the safety of current land-application practices, we distributed questionnaires to 150 individuals concerned about land-application of sewage sludges (Table 2). The group included farmers, residents complaining of adverse health effects, community leaders, and environmentalists. Based on the responses of 87 respondents from 15 states, a majority of respondents (51.7%) desired a total ban on land application of sewage sludges, while 35.6% believed that land application should just be suspended until proven safe. Most respondents (74.7%) lived near land-applications sites and most (67.5%) reported that they had been personally affected by the practice. Overwhelming malodor, vector attraction (flies, mosquitoes), and adverse health effects (e.g., difficulty breathing, chronic sinusitis) were the primary adverse effects reported by individuals living near the sites.

The need for additional research was strongly supported. Respondents, however, expressed little trust in federal and state environmental agencies to provide a reliable scientific evaluation of potential public health and environmental effects. More confidence was expressed if assessments were done by public health agencies, such as the Centers for Disease Control and Prevention (CDC) and the National Institutes of Health (NIH). Although few respondents (16.1%) reported engaging in environmental activism, the group rated environmentalist organizations as being the most trustworthy to assess the safety of land-application practices.

Overall, the survey results indicate that most people concerned about sewage sludge do not believe land application is inherently unsafe but object to the practice because they lack confidence in scientific studies funded by government and industry groups defending the status quo. By contrast, survey respondents indicated a greater level of confidence in studies of land-application practices if done by the CDC or the NIH. It appears, therefore, that overcoming opposition through additional scientific research will require strong involvement with respected public health organizations. It will also require supportive findings from researchers independent of the federal agencies and trade organizations that have historically overseen the development and marketing of land-application practices.

Discussion

Politics of land application. Since the 503 sludge rule (U.S. EPA 1993) was promulgated in 1993, the U.S. EPA, the U.S. Department of Agriculture, and the industry and its trade associations have vigorously defended the rule as fully protective of public health and the environment. The primary basis has been a lack of documented cases of illnesses and the results of research supported with congressional funds earmarked for promoting land application as safe and beneficial (U.S. EPA 2002).

In 2000, the Committee on Science in the U.S. House of Representatives held hearings into allegations that the U.S. EPA retaliates against scientists and private citizens who report adverse environmental and health effects associated with sewage sludge (U.S. House of Representatives 2000a, 2000b).

During the hearings, the U.S. EPA Office of the Inspector General released a report confirming that concerns were widespread among U.S. EPA scientists who reviewed the 503 rule (U.S. EPA 2002). The assistant administrator refused to approve the rule without a major commitment from the Office of Water to support additional in-house research within the Office of Research and Development. The Inspector General noted that this research was never carried out.

The U.S. EPA responded to the congressional hearings by calling for a study by the National Research Council; Congress debated, and overwhelmingly passed, the No Fear Act (Notification and Federal Employee Antidiscrimination and Retaliation Act of 2002). The act, which was aimed at better protecting employees against retaliation, was signed by President Bush last year. The NRC

published its findings and recommendations in July 2002 (NRC 2002), and the U.S. EPA addressed them in a research strategy in the Federal Register earlier this year (U.S. EPA 2003a). The U.S. EPA's final response to the NRC report is due to be released in January 2004. In the meantime, the U.S. EPA Office of Water has provided a docket for public comments (U.S. EPA 2003b).

Public comments to the Office of Water docket have largely mirrored those in the survey we report in this article. There is an overall lack of confidence in the the U.S. EPA's willingness to conduct or support objective research in this area. As evidence, the Sierra Club (San Francisco, CA) and others pointed to the fact that the Office of Water intends to address the NRC recommendations extramurally by funding the same researchers it has historically supported with congressional appropriations for promoting the safety of biosolids. The NRC study (NRC 2002), therefore, had its beginning and ending rooted in controversy over the U.S. EPA using congressional appropriations to support federal policies on the beneficial reuse of sewage sludge and to oppose scientists and private citizens who question them.

Trends in land application. With increasing numbers of residents who live near sludged fields reporting respiratory and gastrointestinal illnesses (Shields 2003), many local governments have banned land application of Class B sewage sludges. However, we found that some Class A sludges generate the same complaints and concluded that going to Class A products will not resolve the pathogens issue (Lewis and Gartie 2002). The reason for this is that infections appear to be primarily opportunistic, following irritation of the skin, mucous membranes, and respiratory tract by chemical components.

Consequently, an important aspect of preventing infections lies in reducing levels of microbial toxins and other chemicals that cause inflammation as well as other responses that predispose individuals to infection. As such, the infections arise from many sources, both community and environmental. The problem with Class A sludges is probably primarily endotoxin related. This is because gram-negative bacteria comprise much of the biomass and because most conditions used to kill bacteria in treatment processes are insufficient to break down endotoxins. The Class A standard, therefore, while reducing the risks of acquiring infections directly from processed sludge, could increase risks of infections from other environmental and community sources.

One outcome of local bans is that land application of sewage sludge is being forced out of areas where residents have the political and economic resources to oppose the practice and into economically depressed areas. Whether this is intentional or not, sewage sludge is being dumped more and more into those communities least able to have their complaints heard, and where residents are least capable of relocating or obtaining medical treatment.

The changing demographics of land application of sewage sludge, therefore, need to be studied. First, census data should be used to assess the socioeconomic makeup of communities living near land-application sites (< 1 km away). Steps then need to be taken to ensure that land-application practices do not disproportionately impact low-income and minority communities.

Recommendations

We recommend that the U.S. EPA undertake and complete five top-priority measures by January 2006 to address the immediate adverse health and environmental effects associated with land-applied sewage sludges:

* Develop a universal high-level disinfection standard to replace the current Class A/ Class B standards, and require industry to provide efficacy data showing treatment methods meet this standard for sporocidal, fungicidal, bactericidal, tuberculocidal, virucidal, anti-protozoal, and anti-parasitic activity

* Develop treatment methods and land management practices for reducing airborne endotoxin levels associated with processed sewage sludges and set limits for public exposure. (We recommend that maximum levels be set at 0.1 times the limit recommended for 10-hr occupational exposure for preventing airway inflammation, which would be 20 EU/[m.sup.3].)

* Conduct a national assessment of groundwater contamination from pathogens, microbial (bacterial, fungal) toxins, organic chemicals, and metals at land-application sites

* Require that industry ensure that land-application practices do not disproportionately target low-income and minority subpopulations in rural communities

* Work with the National Biosolids Partnership (Association of Metropolitan Sewerage Agencies, U.S. EPA, and the Water Environment Federation) to develop and enforce a policy supporting open competition for research funding and prohibiting discrimination and retaliation against individuals raising concerns over adverse environmental and health effects from land-applied sewage sludges.

Table 1. Disinfection levels required to kill pathogens in
sewage sludges. (a)

                                                    Disinfection level
Group                                                    required

Bacterial endospores (e.g., Bacillus anthracis)     High
Nonenveloped viruses (e.g., Norovirus, Coxsackie,
  Botavirus)                                        Intermediate/high
Helminths (e.g., Ascans, Toxocara)                  Intermediate
Protozoa (e.g., Cryptosporidium, Giardia)           Intermediate
Mycobacteria (e.g., M. tuberculosis)                Intermediate
Fungi (e g., Candida)                               Low/intermediate
Vegetative bacteria (e.g., Staphylococcus,
  Salmonella)                                       Low
Enveloped viruses (e.g., hepatitis B, HIV,
  influenza)                                        Low

Data from the Association for the Advancement of Medical
Instrumentation (AAMI 1994).

(a) Disinfection levels are based on susceptibilities to liquid
chemical germicides; groups increase similarly in resistance to heat,
with enveloped viruses being the most sensitive and bacterial
endospores the most resistant.

Table 2. Summary of survey results from 87 respondents indicating
their level of public concern about land application practices.

Topic          Question

Background     Why are you interested
information    in the issue of land-applied
(a)            sewage sludges?

               Have you ever been personally
               affected by land application of
               sewage sludges?

               How do you think land application
               of sewage sludges should be
               handled?

Level of       On a scale of 0 to 10 (0 = no concern;
concern (b)    10 = highest level of concern), indicate
               your level of concern regarding the
               following issues

               Kinds of contamination from sludges
               that cause the most concern (0 = no
               concern; 10=highest level
               of concern)

Level of       Using a scale of 0 to 10 (0 = no trust,
trust (b)      10 = highest level of trust)
               indicate your level of trust in organizations
               dealing with land application of
               sewage sludges

Need for       On a scale of 0 to 10 (0 = don't feel that
additional     more research is needed, 10 = feel very
research (b)   strongly that more research is needed),
               indicate how strongly you feel that more
               scientific research is needed before we
               will know whether land applying sewage
               sludges is safe for public health and
               the environment

               On a scale of 0 to 10 (0 = no trust,
               10 = highest level of trust),
               indicate your level of trust in the work
               of scientists supported by various
               organizations dealing with land
               application of sewage sludges

                                                   Percent or mean
Topic          Choices                              [+ or -] SD (n)

Background     Live or lived near land
information      application site                           74.7% (87)
(a)            Work as a farmer/grower                       4.6% (87)
               Engaged in environmental
                 activism                                   16.1% (87)
               Other                                        14.9% (87)
               Yes                                          67.5% (77)

               Current practices are safe;no
                 new restrictions are needed                   0% (87)
               All land application should be
                 completely banned                          51.7% (87)
               Only certain land application
                 practices should be banned                  8.0% (87)
               All land application should be
                 suspended until proven safe                35.6% (87)
               Land application should be
                 continued with certain new
                 restrictions                                2.3% (87)
               Other                                         5.7% (87)

Level of       Microorganisms that may cause
concern (b)      infection                       9.7 [+ or -] 0.9 (83)
               Chemicals, metals and
                 microorganism that may cause
                 cancer                          9.6 [+ or -] 1.0 (84)
               Odor-causing emissions            8.9 [+ or -] 1.9 (84)
               Bacterial toxins                  9.7 [+ or -] 9.8 (82)
               Property value                    8.6 [+ or -] 2.3 (82)
               Other                             9.7 [+ or -] 0.7 (25)

               Contamination of food supply      9.3 [+ or -] 1.4 (83)
               Contamination of water            9.9 [+ or -] 0.7 (84)
               Contamination of soil             9.8 [+ or -] 0.5 (84)
               Contamination of air              9.6 [+ or -] 1.0 (84)
               Other                             9.8 [+ or -] 0.5 (26)

Level of       Congress                          2.0 [+ or -] 2.3 (81)
trust (b)      U.S. EPA                          1.3 [+ or -] 2.4 (82)
               U.S. Department of Agriculture    1.7 [+ or -] 2.5 (80)
               State agencies                    1.2 [+ or -] 2.1 (81)
               Local governments (city/county)   2.4 [+ or -] 3.1 (81)
               Environmental organizations       7.0 [+ or -] 2.8 (81)
               Trade groups (e.g., WEF, NEBRA)   0.8 [+ or -] 2.1 (75)
               National Biosolids Partnership    0.5 [+ or -] 1.7 (72)
               Industry                          0.5 [+ or -] 1.5 (80)
               Other (c) (e.g., departments of
                 health, independent
                 scientists)                     5.3 [+ or -] 4.4 (19)

Need for                                         9.6 [+ or -] 1.7 (84)
additional
research (b)   National Science Foundation/
                 National Institutes of Health   5.1 [+ or -] 3.3 (72)
               Trade groups (WEF/WERF)           1.4 [+ or -] 2.2 (72)
               U.S. EPA Office of Water          1 4 [+ or -] 2.4 (77)
               U S. EPA Office of Research and
                 Development                     2.8 [+ or -] 3.1 (75)
               U.S. Department of Agriculture    1.8 [+ or -] 2.6 (76)
               Centers for Disease Control and
                 Prevention                      4.9 [+ or -] 3.4 (75)
               Industry                          0.5 [+ or -] 1.4 (76)
               State agencies                    1.2 [+ or -] 2.1 (78)
               Other (c) (e g., universities,
                 independent scientists,
                 environmental groups)           5.9 [+ or -] 4.7 (19)

Abbreviations: NEBRA, New England Biosolids and Residuals Association;
WEF, Water Environment Federation; WERF, Water Environment Research
Federation. Responses not following survey instructions were omitted.

(a) Based on yes/no responses from all 87 respondents; values shown
are percent = SO (n). (b) Based on a 0-10 scale, with averages
determined from the actual number of responses to each category;
values shown are mean [+ or -] SD (n). (c) Categories given by
respondents.

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Gloria D. Coronado, (1) Beti Thompson, (1) Larkin Strong, (1) William C. Griffith, (2) and Ilda Islas (1)

(1) Cancer Prevention Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington, USA; (2) Department of Environmental Health, School of Public Health and Community Medicine, University of Washington, Seattle, Washington, USA

Address correspondence to G.D. Coronado, P.O. Box 19024, 1100 Fairview Avenue N, MP-702, Seattle, WA 98109 USA. Telephone: [phone]. Fax: [phone]. E-mail: [e-mail]

We acknowledge the contribution of members of our community advisory board in designing and carrying out the project. We thank C, Curl, R. Fenske, and J. Kissel for processing the urine and dust samples for this study.

The research described in this article has been funded in part by the by the U.S. Environmental Protection Agency (grant R826886) and the National Institutes of Health (grant P01 ES09601), but it has not been subjected to either agency's required peer and policy review. The article does not necessarily reflect the views of either agency, and no official endorsement should be inferred.

The authors declare they have no competing financial interests.

Received 25 April 2003; accepted 22 October 2003.