The Agricultural Health Study: factors affecting completion and return of self-administered questionnaires in a large prospective cohort study of pesticide applicators

Response rates were examined in a prospective epidemiologic study of individuals, mostly farmers, from Iowa and North Carolina seeking a pesticide applicator license during the period from 1994 through 1996. In the first year of enrollment 16,535 farmers (representing 77% of eligible farmer applicators) enrolled in the study by completing a 17-page questionnaire administered at a pesticide training session; 47% of the enrolled farmers completed and returned a much longer take-home questionnaire. The characteristics of farmers who completed only the enrollment questionnaire were quite similar to those of farmers who also completed and returned the take-home questionnaire. The most notable difference was the increased age of responders. Thus, the study population might have slightly higher cumulative farm exposures and slightly lower current farm exposures than the base population of all farmer applicators. The lack of evidence for substantial selection bias is reassuring for the Agricultural Health Study, and provides a measure of reassurance for other studies depending on the voluntary completion of self-administered questionnaires.

Avoided and avoidable risks of cancer

Despite the considerable efforts and funds devoted to cancer research over several decades, cancer still remains a mainly lethal disease. Cancer incidence and mortality have not declined at the same rate as other major causes of death, indicating that primary prevention remains a most valuable approach to decrease mortality. There is general agreement that environmental exposures are variously involved in the causation of the majority of cancer cases and that at least half of all cancers could be avoided by applying existing etiologic knowledge. There is disagreement, however, regarding the proportion of cancer risks attributable to specific etiological factors, including diet, occupation and pollution. Estimates of attributable risks are largely based today on unverified assumptions and the calculation of attributable risks involves taking very unequal evidence of various types of factors and treating them equally. Effective primary prevention resulting in a reduction of cancer risk can be obtained by: (i) a reduction in the number of carcinogens to which humans are exposed; or (ii) a reduction of the exposure levels to carcinogens. Exposure levels that could be seen as sufficiently low when based on single agents, may actually not be safe in the context of the many other concomitant carcinogenic and mutagenic exposures. The list of human carcinogens and of their target organs might be quite different if: (i) epidemiological data were available for a larger proportion of human exposures for which there is experimental evidence of carcinogenicity; (ii) more attention was paid to epidemiological evidence that is suggestive of an exposure-cancer association, but is less than sufficient, particularly in identifying target organs; and (iii) experimental evidence of carcinogenicity, supported by mechanistic considerations, were more fully accepted as predictions of human risk.

The challenges of assessing outcome in chronic pain

Clinicians in chronic pain services are facing the need to develop meaningful and methodologically adequate measures, not only to evaluate the effectiveness of interventions and to assure quality, but also to support the continued funding and future development of such services. Explores the problems inherent in assessing outcomes in chronic pain. These include the complexity of the chronic pain syndrome itself, the multidimensional nature of interventions and the challenges of defining outcomes in the chronic illness syndrome. The complexity and challenges of assessing outcomes may lead to some reticence in facing the challenges but it is the responsibility of the clinicians to continue developing measures and to communicate to purchasers and other stake holders the complexity of assessing outcomes in chronic pain.

Occupational epidemiologic study design and application

Occupational epidemiologic investigations have provided, and will continue to provide, important information to understand environmental causes of disease. High-quality investigations designed to test hypotheses have several requirements. They must include valid quantitative assessments of exposure, some information on lifestyle risk factors, and include biologic monitoring and marker components whenever possible. Availability of these data allows a clear evaluation of potential confounders and biases, assessment of interaction among risk factors, and provides the opportunity to identify susceptible subgroups.

Newborn screening for HLA markers associated with IDDM: diabetes autoimmunity study in the young (DAISY)

Autoimmunity causing insulin-dependent diabetes mellitus (IDDM) begins in early childhood due to interactions between genes and unknown environmental factors that may be identified through follow-up of a large cohort of genetically susceptible children. Such a cohort has been established using a simple and rapid cord blood screening for HLA alleles. The DRB1 and DQB1 second exon sequences were co-amplified using the polymerase chain reaction and hybridized with single and pooled sequence-specific oligonucleotide probes. Four individual probes were used to detect the susceptibility alleles DRB1*03, DRB1*04, and DQB1*0302 as well as the usually protective DRB1*15/16 (DR2) alleles. In addition, pooled probes allow the distinction of DR3/3 from the DR3/x genotype (where x is neither DR2, 3, nor 4) and DR4/4 from DR4/x. Among 5000 newborns from the general Denver population, we have found the high-risk genotype (DRB1*03/ DRB1*04, DQB1*0302) to be present in 2.4% of non-Hispanic whites, 2.8% of Hispanics, and 1.6% of African Americans. The moderate-risk genotypes (DRB1*04, DQB1*0302/DRB1*04, DQB1*0302, DRB1*04, DQB1*0302/x, or DRB1*03/DRB1*03) are present in 17% of American non-Hispanic whites, 24% of Hispanics and in 10% of African Americans. These results demonstrate the feasibility of a large-scale newborn screening for genes associated with IDDM. The ultimate role for such a screening in future routine prediction and prevention of IDDM will depend on the availability of an effective and acceptable form of clinical intervention.

Beta-cell autoantibodies in infants and toddlers without IDDM relatives: diabetes autoimmunity study in the young (DAISY)

Little is known concerning the natural history of beta-cell autoimmunity in infants and toddlers, especially in those without a first degree IDDM relative. A population-based cohort of Colorado infants at increased IDDM risk due to their HLA genotype has been identified through a PCR-based HLA screening of cord blood and is being prospectively studied. We report the distribution of insulin (IAA), GAD65 (GAA), and ICA512 autoantibody levels in 312 children aged 9 months and in 131 children aged 15 months from this cohort, without family history of IDDM. The levels of IAA, GAA and ICA512 did not differ by the HLA genotype (DR3/4,DQB1*0302 vs. DR3/3, vs. DR2/DR4,DQB1*0302 vs. DRx/4,DQB1*0302, where x is not DR3 or DR2), by ethnicity (non-Hispanic whites vs. other ethnic groups), or by age (9 vs. 15 months). The 95th and 99th percentiles of the IAA distribution were respectively 40 and 61 nU/ml at the age of 9 months and 38 and 59 nU/ml at the age of 15 months. The 95th and 99th percentiles of the GAA distribution were respectively 0.020 and 0.046 at the age of 9 months and 0.022 and 0.098 at the age of 15 months. We propose to use IAA levels greater than 60 nU/ml and GAA index greater than 0.05 to define the presence of beta-cell autoimmunity in children younger than 2 years.

Characterization of a hierarchy in human acute myeloid leukemia progenitor cells

Despite the usual uniform and primitive appearance of cells derived from the leukemic clone in most patients with acute myeloid leukemia (AML), there is considerable heterogeneity among leukemic blasts, particularly with respect to their capacity to proliferate and/or self renew. We have assessed whether these differences in proliferative potential are correlated with the phenotypic changes that characterize normal hematopoiesis, which might suggest an analogous hierarchy of AML progenitors. We have used the ability of primitive AML cells to persist or produce blast colony forming cells (CFU-blast) detected after 2 to 8 weeks in the presence of growth factors in suspension cultures (SC) termed SC-initiating cells (IC), or with stroma in long-term cultures (LTC-IC) as a quantitative assay for a cell that may have primitive characteristics. This SC assay is linear, cell concentration independent, and the frequency of SC-IC by limiting dilution analysis is lower than primary CFU-blast. The average output of CFU-blast after 2 to 8 weeks by individual SC-IC varied between 2 and more than 100 in individual patients. Leukemic blasts were sorted based on their expression of antigens previously found useful to characterize normal progenitor differentiation, and analyzed for the percentage of CFU-blast SC-IC, and leukemic LTC-IC within each fraction. All of these progenitor types were heterogeneous in their expression of CD45RA and CD33, but expressed uniformly low levels of CD15 and differed from normal primitive progenitors in their high expression of HLA-DR. CFU-blast had a significantly higher expression of CD71 and CD38 as compared with SC-IC or leukemic LTC-IC. In patients with CD34+ blasts, the majority of their SC-IC at 4 weeks were CD34+/CD38-; however, patients with CD34- blasts had at least some CD34- progenitors. These results show that while heterogeneity exists between patients, it is possible to physically separate subpopulations of AML cells with different proliferative potentials. It also provides some support for the concept that quantitation of leukemic cells capable of producing CFU-blast for 4 weeks or more in vitro measures a less frequent leukemic progenitor with higher proliferative potential that may be the only relevant cell for maintaining the leukemic clone in vivo.

Regulation of two pair-rule stripes by a single enhancer in the Drosophila embryo

Previous studies on the regulation of the segmentation gene even-skipped (eve) have centered on the transcription of stripe 2. Here, we characterize another enhancer module contained within the complex eve promoter that directs expression of stripes 3 and 7. This enhancer is approximately 500 bp in length and maps approximately 3.3 kb upstream of the transcription start site. The stripe 3 + 7 enhancer appears to be regulated by one or more ubiquitously distributed activators, including components of a JAK-Stat pathway. The two-stripe pattern results via multiple tiers of repressors which delimit this ubiquitous activation. The zinc finger repressor hunchback appears to be responsible for establishing the anterior border of stripe 3 and the posterior border of stripe 7. knirps, a member of the nuclear receptor family of transcription factors, appears to establish the posterior border of stripe 3 and the anterior border of stripe 7. Activator and repressor proteins bind in vitro to several sites within the enhancer. These findings suggest a general model for the regulation of segmentation stripes, whereby enhancers integrate positional information provided by broadly distributed activators and spatially restricted repressors.

The Agricultural Health Study

The Agricultural Health Study, a large prospective cohort study has been initiated in North Carolina and Iowa. The objectives of this study are to: 1) identify and quantify cancer risks among men, women, whites, and minorities associated with direct exposure to pesticides and other agricultural agents; 2) evaluate noncancer health risks including neurotoxicity reproductive effects, immunologic effects, nonmalignant respiratory disease, kidney disease, and growth and development among children; 3) evaluate disease risks among spouses and children of farmers that may arise from direct contact with pesticides and agricultural chemicals used in the home lawns and gardens, and from indirect contact, such as spray drift, laundering work clothes, or contaminated food or water; 4) assess current and past occupational and nonoccupational agricultural exposures using periodic interviews and environmental and biologic monitoring; 5) study the relationship between agricultural exposures, biomarkers of exposure, biologic effect, and genetic susceptibility factors relevant to carcinogenesis; and 6) identify and quantify cancer and other disease risks associated with lifestyle factors such as diet, cooking practices, physical activity, smoking and alcohol consumption, and hair dye use. In the first year of a 3-year enrollment period, 26,235 people have been enrolled in the study, including 19,776 registered pesticide applicators and 6,459 spouses of registered farmer applicators. It is estimated that when the total cohort is assembled in 1997 it will include approximately 75,000 adult study subjects. Farmers, the largest group of registered pesticide applicators comprise 77% of the target population enrolled in the study. This experience compares favorably with enrollment rates of previous prospective studies.

Agricultural exposures and cancer

The purpose of this report is to review the literature on cancer among persons employed in agriculture, to characterize the value of this line of research, and to recommend future directions. Farmers, despite a generally favorable mortality, appear to experience elevated rates for several cancers, including leukemia, non-Hodgkin's lymphoma, multiple myeloma, soft-tissue sarcoma, and cancers of the skin, lip, stomach, brain, and prostate. The rates for several of these tumors (i.e., non-Hodgkin's lymphoma, multiple myeloma, skin, brain, and prostate) appear to be increasing in the general population. No set of established etiologic factors explains all the cancer excesses observed among farmers, although several are associated with naturally occurring or medically induced immunodeficiencies. This suggests that there may be factors in the agricultural environment that introduce immune system deficiencies. Farmers are exposed to a variety of substances that could operate through this mechanism, including pesticides, engine exhausts, solvents, dusts, and zoonotic microbes. Studies to further characterize the cancer risk among farmers, their dependents, and farm laborers, and to identify the exposures that may be involved would not only be useful in providing a safe work environment in agriculture but may furnish considerable insight into the causes for a number of tumors that are rising in incidence in the general population.

Guidelines for application of meta-analysis in environmental epidemiology. ISLI Risk Science Institute

The use of meta-analysis in environmental epidemiology can enhance the value of epidemiologic data in debates about environmental health risks. Meta-analysis may be particularly useful to formally examine sources of heterogeneity, to clarify the relationship between environmental exposures and health effects, and to generate information beyond that provided by individual studies or a narrative review. However, meta-analysis may not be useful when the relationship between exposure and disease is obvious, when there are only a few studies of the key health outcomes, or when there is substantial confounding or other biases which cannot be adjusted for in the analysis. Recent increases in the use of meta-analysis in environmental epidemiology have highlighted the need for guidelines for the application of the technique. Guidelines, in the form of desirable and undesirable attributes, are presented in this paper for various components of a meta-analysis including study identification and selection; data extraction and analysis; and interpretation, presentation, and communication of results. Also discussed are the appropriateness of the use of meta-analysis in environmental health studies and when meta-analysis should or should not be used.

United States non-Hodgkin's lymphoma surveillance by occupation 1984-1989: a twenty-four state death certificate study

Death certificates from 23,890 male and female non-Hodgkin's lymphoma (NHL) cases and 119,450 noncancer controls from 24 states for the period 1984-1989 were used to generate hypotheses regarding occupational associations. Cases were frequency matched by age, race, and gender with five controls per case. Odds ratios were calculated for 231 industries and 509 occupations. Significant associations were observed for a variety of white-collar professionals (i.e., real estate agents, secretaries, bookkeepers, teachers, postal employees, business agents, engineers, chemists, and medical professionals) and blue-collar occupations (i.e., firefighters, farm managers, aircraft mechanics, electronic repairers, mining machine operators, and crane and tower operators).

Pooled reanalysis of cancer mortality among five cohorts of workers in wood-related industries

OBJECTIVES

To provide more information regarding the risk of cancer associated with wood dust, a pooled reanalysis of data from five cohort studies was performed.

METHODS

The combined cohort consisted of 28,704 persons from five studies: British furniture workers, members of the union representing furniture workers in the United States, two cohorts of plywood workers, and one of wood model makers, among whom 7665 deaths occurred. Pooled analyses were carried out for all of the cohorts combined, the two furniture worker cohorts combined, and the two plywood workers cohorts combined.

RESULTS

Significant excesses of nasal [observed 11, standardized mortality ratio (SMR) 3.1, 95% confidence interval (95% CI) 1.6-5.6] and nasopharyngeal (observed 9, SMR 2.4, 95% CI 1.1-4.5) cancer were observed. That for nasal cancer appeared to be associated with exposure to wood dust but was based solely on cases from the British furniture worker cohort, while that of nasopharyngeal cancer was observed for furniture and plywood workers and was associated with both high and low probability of wood dust exposure. Some support for an excess risk of multiple myeloma was also observed but was less clearly associated with wood dust exposure. No excesses of lung, larynx, stomach, or colon cancer were found to be associated with any surrogate indicators of wood dust exposure.

CONCLUSIONS

Workers exposed to wood dust may have an excess risk of nasopharyngeal cancer and multiple myeloma in addition to sinonasal cancer. The limitations of this study would tend to obscure relationships, rather than create false positive findings.

Cancer and noncancer risk to women in agriculture and pest control: the Agricultural Health Study

The Agricultural Health Study is a collaborative effort involving the National Cancer Institute, the US Environmental Protection Agency, and the National Institute of Environmental Health Sciences. A goal of this investigation is to establish a large cohort of men and women that can be followed prospectively for 10 years or more to evaluate the role of agricultural exposures in the development of cancer, neurologic disease, reproductive difficulties, childhood developmental problems, and other chronic diseases. The study also will provide an opportunity to assess the role that diet, cooking methods, and other lifestyle factors have on the cause of cancer and other diseases. The cohort will be composed of approximately 112,000 adult study subjects, including 42,000 women, making this one of the largest cohorts of women ever assembled for an epidemiologic investigation of environmental and occupational exposures. Children of farm families also will be enrolled. The study will be conducted in Iowa and North Carolina. Enrollment will begin in December 1993 and continue for 3 years.

Occupational cancer mortality among women employed in the telephone industry

We conducted a mortality odds ratio (MOR) analysis among women employed in the telephone industry, using death certificates from 24 reporting states for 1984 through 1989. Usual occupation and industry from the death certificates were coded using the 1980 Bureau of the Census occupational and industrial classification system. There were 2444 cancer deaths among women in the telephone industry (code 441). Among younger (age < 49) white women, significant excess risks were observed from cancers of the rectum (MOR = 3.3; 95% confidence interval [CI] = 1.2 to 8.7), connective tissue (MOR = 4.4; 95% CI = 2.2 to 8.8), breast (MOR = 1.6; 95% CI = 1.3 to 2.1), corpus uteri (MOR = 3.3; 95% CI = 1.5 to 7.5), ovary (MOR = 2.1; 95% CI = 1.3 to 3.5), and brain (MOR = 2.1; 95% CI = 1.2 to 3.7). Cancer of the connective tissue showed an almost sixfold risk (MOR = 5.5; 95% CI = 2.0 to 14.8) for the age group of 30 to 39 years. Excess risks of cancer of the connective tissue were observed among engineers and technicians, office workers, telephone operators, and mechanics and repairers (MOR = 8.5, 4.9, 1.7, and 4.4, respectively), suggesting a possible relationship with modern technological exposures in the telephone industry. Risks for cancers of the breast, corpus uteri, ovary, and brain were also elevated among these jobs. We did not have information on other risk factors for these cancer sites; therefore, socioeconomic status or lifestyle may explain these observed associations, particularly for the cancers of the reproductive system.(ABSTRACT TRUNCATED AT 250 WORDS)

Risk of multiple myeloma by occupation and industry among men and women: a 24-state death certificate study

This cancer surveillance investigation uses death certificates from 24 states for the period 1984-1989 to identify multiple myeloma and occupation associations and to stimulate hypotheses. A case-control study of multiple myeloma was created from 3,159,417 certificates in which 12,148 male and female cases were frequency matched by age, race, and gender with five controls per case. We screened 231 industries and 509 occupations. Women demonstrated significant excess risk among managers and administrators, post-secondary teachers, elementary teachers, social workers, other sales workers, waitresses, and hospital maids. Men showed significant risks among computer system scientists, veterinarians, elementary teachers, authors, engineering technicians, general office supervisors, insurance adjusters, barbers, electronic repairers, supervisors of extracting industries, production supervisors, photoengravers, and grader/dozer operators. Men and women elementary school teachers demonstrated the most consistent, statistically significant increased risk of multiple myeloma.

Dietary factors and non-Hodgkin's lymphoma in Nebraska (United States)

Little is known about dietary factors and non-Hodgkin's lymphoma (NHL) risk, although high intakes of animal protein and milk have been associated with NHL in two previous studies. As part of a population-based case-control study of agricultural and other risk factors for NHL in eastern Nebraska (USA), we examined the self- and proxy-reported frequency of consumption of 30 food items by 385 White men and women with NHL and 1,432 controls. Animal protein intake was not associated significantly with the risk of NHL, however, there was a nonsignificantly elevated risk of NHL among men with high milk consumption. Vitamin C, carotene, citrus fruit, and dark green vegetable intakes were inversely significantly related to the risk of NHL for men, but not for women. Among men, the odds ratios for the highest quartiles of both vitamin C and carotene intake were 0.6 (95% confidence intervals = 0.3-1.0). There were no meaningful differences in the associations of nutrient intakes and NHL risk between B- and T-cell lymphomas and histologic types. Risks for low intakes of vitamin C and carotene were greater among men and women with a family history of cancer, particularly a history of lymphatic or hematopoietic cancer among first-degree relatives.

Occupational exposure to chlorinated aliphatic hydrocarbons and risk of astrocytic brain cancer

Chlorinated aliphatic hydrocarbons (CAHs) were evaluated as potential risk factors for astrocytic brain tumors. Job-exposure matrices for six individual CAHs and for the general class of organic solvents were applied to data from a case-control study of brain cancer among white men. The matrices indicated whether the CAHs were likely to have been used in each industry and occupation by decade (1920-1980), and provided estimates of probability and intensity of exposure for "exposed" industries and occupations. Cumulative exposure indices were calculated for each subject. Associations of astrocytic brain cancer were observed with likely exposure to carbon tetrachloride, methylene chloride, tetrachloroethylene, and trichloroethylene, but were strongest for methylene chloride. Exposure to chloroform or methyl chloroform showed little indication of an association with brain cancer. Risk of astrocytic brain tumors increased with probability and average intensity of exposure, and with duration of employment in jobs considered exposed to methylene chloride, but not with a cumulative exposure score. These trends could not be explained by exposures to the other solvents.