Concomitant and antecedent deep venous thrombosis and cancer survival in male US veterans

Survival is reportedly worse in patients with cancer concurrently diagnosed with deep venous thrombosis. However, information on specific malignancies is limited. From a cohort study of male US veterans we identified incident cancer cases (n = 412,008) and compared survival patterns among those with versus without a history of deep venous thrombosis. Using Cox proportional hazard models, we estimated hazard ratios (HRs) and 95% confidence intervals as measures of the relative risk of dying. Individuals with (versus without) a concomitant deep venous thrombosis and cancer diagnosis had a higher risk of dying (HR = 1.38; 1.28-1.49). The most prominent excess mortality (HR = 1.29-2.55) was observed among patients diagnosed with deep venous thrombosis at the time of diagnosis of lung, gastric, prostate, bladder, or kidney cancer. Increased risk of dying was also found among cancer patients diagnosed with deep venous thrombosis 1 year (HR = 1.14; 1.07-1.22), 1-5 years (HR = 1.14; 1.10-1.19), and >5 years (HR = 1.27; 1.23-1.31) before cancer; this was true for most cancer sites (HR = 1.17-1.64). In summary, antecedent deep venous thrombosis confers a worse prognosis upon cancer patients. Advanced stage at diagnosis, treatment effects, lifestyle factors, and comorbidity could explain differences by cancer site and time frame between a prior deep venous thrombosis diagnosis and cancer outcome.

The Measurement of the Radial Stiffness of Rolling Element Bearings under Oscillating Conditions

There is very little information available on the characteristics of rolling element bearings under oscillating conditions. This is because of the difficulty that has been experienced in measuring the relevant characteristics. A rig is described which is very simple in principle and allows the measurement of the radial stiffness of a pair of bearings. For the angular contact bearings tested the levels of damping obtained are larger than previously expected.

An Investigation of the Transient Effects during Variable Speed Cutting

Conventionally the stability analysis of machine tools is restricted to determining if a particular operation will become unstable. The transient behaviour is not examined in any further detail. However, under certain conditions larger transient vibrations occur even though the process may ultimately be stable. A method of prediction of transient behaviour is presented and applied to variable speed cutting on a lathe where such transients are significant.

A Vibration Technique for Non-Destructively Assessing the Integrity of Structures

A method of non-destructively evaluating the integrity of structures is described and applied to structures for which a one dimensional analysis is satisfactory. It is shown how vibration measurements made at a single station in the structure can be used, in conjunction with a suitable theoretical model, to indicate both the location and the magnitude of a defect. Receptance analysis is used in this instance, but the principle is equally applicable to other techniques of mathematical analysis.

Experimental results are obtained on a variety of components, including straight prismatic bars, a doubly-tapered bar, and an automobile camshaft, excellent agreement between the predicted and actual damage sites being obtained. The axial mode of vibration is generally used, although somes tests are also carried out successfully in torsion.

CYP1A1 and GSTM1 polymorphisms in relation to lung cancer risk in Chinese women

We examined CYP1A1 (I462V) and GSTM1 null polymorphisms in 200 female cases and 144 female controls selected from a population-based case-control study of lung cancer conducted in northeast China, where the rates of lung cancer among Chinese women are especially high. The CYP1A1 codon 462 point mutation in exon 7 (I462V) causes an Ile-Val substitution near the heme binding site. This mutation correlates with inducibility of aryl hydrocarbon hydrolase (AHH) activity, which activates polycyclic aromatic hydrocarbons (PAHs) in tobacco smoke and in indoor air pollution from coal-burning stoves, a risk factor for lung cancer in this study population. We found that the CYP1A1 I462V genotype (combined ile/val and val/val) was significantly associated with lung cancer risk. The odds ratio (OR) was 2.5 (95% confidence interval [CI], 1.55-4.03) after adjustment for significant risk factors such as age, ever smoking status, family history of cancer, and eye irritation when cooking. The association was more pronounced among non-smokers (OR=3.67; 95% CI, 1.85-7.28) than among smokers (OR=1.74, 95% CI, 0.85-3.54). In contrast, we did not find a significant association with the GSTM1 null genotype. In summary, our case-control study of lung cancer among women in northeast China revealed an elevated risk associated with the CYP1A1 I462V genotype, but no interaction with smoking or indoor air pollution was found.

Occupation and prostate cancer risk in Sweden

To provide new leads regarding occupational prostate cancer risk factors, we linked 36,269 prostate cancer cases reported to the Swedish National Cancer Registry during 1961 to 1979 with employment information from the 1960 National Census. Standardized incidence ratios for prostate cancer, within major (1-digit), general (2-digit), and specific (3-digit) industries and occupations, were calculated. Significant excess risks were seen for agriculture-related industries, soap and perfume manufacture, and leather processing industries. Significantly elevated standardized incidence ratios were also seen for the following occupations: farmers, leather workers, and white-collar occupations. Our results suggest that farmers; certain occupations and industries with exposures to cadmium, herbicides, and fertilizers; and men with low occupational physical activity levels have elevated prostate cancer risks. Further research is needed to confirm these findings and identify specific exposures related to excess risk in these occupations and industries.

Respiratory cancer in a cohort of copper smelter workers: results from more than 50 years of follow-up

Several studies have linked inhalation of airborne arsenic with increased risk of respiratory cancer, but few have analyzed the shape of the exposure-response curve. In addition, since inhaled airborne arsenic affects systemic levels of inhaled arsenic, there is concern that inhaled arsenic may be associated with cancers of the skin, bladder, kidney, and liver, which have been linked to ingested arsenic. The authors followed 8,014 white male workers who were employed for 12 months or more prior to 1957 at a Montana copper smelter from January 1, 1938 through December 31, 1989. A total of 4,930 (62%) were deceased, including 446 from respiratory cancer. Significantly increased standardized mortality ratios (SMRs) were found for all causes (SMR = 1.14), all cancers (SMR = 1.13), respiratory cancer (SMR = 1.55), diseases of the nervous system and sense organs (SMR = 1.31), nonmalignant respiratory diseases (SMR = 1.56), emphysema (SMR = 1.73), ill-defined conditions (SMR = 2.26), and external causes (SMR = 1.35). Internal analyses revealed a significant, linear increase in the excess relative risk of respiratory cancer with increasing exposure to inhaled airborne arsenic. The estimate of the excess relative risk per mg/m3-year was 0.21/(mg/m3-year) (95% confidence interval: 0.10, 0.46). No other cause of death was related to inhaled arsenic exposure.

The Legionella pneumophila prp locus; required during infection of macrophages and amoebae

Transposon mutagenesis was performed using mTn 10phoA to identify Legionella pneumophila genes that are expressed under certain in vitro conditions, and are required for intracellular replication. Of the 1653 PhoA fusions examined, 19 PhoA(+)fusion mutants were isolated and screened for differential expression of fusion proteins after growth at 30 or 37 degrees C, in the presence of low iron, or increased magnesium concentrations. The mutants were examined for their cytopathogenicity and intracellular replication within U937 macrophage-like cells and the protozoan Hartmannella vermiformis. One of the mutants generated, BS10, was defective in its multiplication within U937 macrophage-like cells and H. vermiformis. The defect in BS10 was complemented with a cosmid clone containing the wild type locus. The open reading frame interrupted by the insertion was homologous to prpD of Salmonella typhimurium and mmgE of Bacillus subtilis.

Natural competence for DNA transformation by Legionella pneumophila and its association with expression of type IV pili

We have recently described the expression of two pili of different lengths on the surface of Legionella pneumophila (B. J. Stone and Y. Abu Kwaik, Infect. Immun. 66:1768-1775, 1998). Production of long pili requires a functional pilEL locus, encoding a type IV pilin protein. Since type IV pili in Neisseria gonorrhoeae are associated with competence for DNA transformation, we examined the competence of L. pneumophila for DNA transformation under conditions that allowed the expression of type IV pili. We show that L. pneumophila is naturally competent for DNA transformation by isogenic chromosomal DNA and by plasmid DNA containing L. pneumophila DNA. Many different L. pneumophila loci are able to transform L. pneumophila after addition of plasmid DNA, including gspA, ppa, asd, and pilEL. The transformation frequency is reduced when competing DNA containing either L. pneumophila DNA or vector sequences is added to the bacteria, suggesting that uptake-specific sequences may not be involved in DNA uptake. Competence for DNA transformation correlates with expression of the type IV pili, and a pilEL mutant defective in expression of type IV pili is not competent for DNA transformation. Complementation of the mutant for competence is restored by the reintroduction of a cosmid that restores production of type IV pili. Minimal competence is restored to the mutant by introduction of pilEL alone. We conclude that competence for DNA transformation in L. pneumophila is associated with expression of the type IV pilus and results in recombination of L. pneumophila DNA into the chromosome. Since expression of type IV pili also facilitates attachment of L. pneumophila to mammalian cells and protozoa, we designated the type IV pili CAP (for competence- and adherence-associated pili).

Different fates of Legionella pneumophila pmi and mil mutants within macrophages and alveolar epithelial cells

Alveolar epithelial cells, which constitute the majority of the alveolar surface, may represent a potential niche for intracellular replication of Legionella pneumophila that has been largely overlooked. We examined the phenotypes of a bank of 121 macrophage-defective mutants of L. pneumophila (designated as pmi and mil) for their cytopathogenicity to and intracellular survival and replication within human alveolar epithelial cells. Our data showed that 91 of 121 mutants that were defective (modest-severe) in macrophages exhibited wild type-like phenotypes in human type I alveolar epithelial cells. In contrast, the other 30 mutants were defective in both macrophages and alveolar epithelial cells. Transmission electron microscopy of the intracellular infection by three mutants showed that the defect in intracellular replication in macrophages and epithelial cells was associated with a defect in recruitment of the RER around the phagosome. Differences in attachment to macrophages and epithelial cells were also exhibited by some of the mutants. Pulmonary infection studies of A/J mice showed that a mutant defective in macrophages but not in alveolar epithelial cells replicated like the wild type strain in the lungs of A/J mice. In contrast, a mutant defective in both macrophages and alveolar epithelial cells failed to replicate and was killed. We conclude that certain distinct genetic loci of L. pneumophila are uniquely required for intracellular survival and replication within phagocytic but not epithelial cells, which may be important in vivo.

The incidence of regurgitation during cardiopulmonary resuscitation: a comparison between the bag valve mask and laryngeal mask airway

The risk of gastric regurgitation and subsequent pulmonary aspiration is a recognised complication of cardiac arrest--a risk which may be further increased by the resuscitative procedure itself. The purpose of this study was to compare the incidence of gastric regurgitation between the bag valve mask (BVM) and laryngeal mask airway (LMA). The resuscitation data collection forms of 996 patients who underwent in-hospital cardiopulmonary resuscitation over a 3.5 year period were reviewed. Of these, 199 patients were excluded from the study because there was no airway management involving a BVM or LMA. The incidence and timing of regurgitation was studied in the remaining 797 patients. Regurgitation was recorded to have occurred at some stage in 180 of these patients (22.6%). However, 84 regurgitated prior to CPR (46.7% of those patients who regurgitated). These patients were excluded from further analysis as regurgitation could not have been affected by any form of ventilation. Of the remaining 713 patients, BVM ventilation was used in 636 cases. In 170 of these the LMA was also used following the BVM. Where the patient was ventilated with the BVM alone or BVM followed by ETT the incidence of regurgitation during CPR was 12.4%. The LMA was used during resuscitation in 256 cases of which 170 had BVM ventilation prior to the LMA. Where the patient was ventilated with the LMA alone or LMA followed by ETT the incidence of regurgitation during CPR was 3.5%. The study confirms experience reported in earlier studies that when an LMA is used as a first line airway device, regurgitation is relatively uncommon.

Expression of multiple pili by Legionella pneumophila: identification and characterization of a type IV pilin gene and its role in adherence to mammalian and protozoan cells

Legionella pneumophila expresses pili of variable lengths, either long (0.8 to 1.5 microm) or short (0.1 to 0.6 microm), that can be observed by transmission electron microscopy. We have identified a gene in L. pneumophila with homology to the type IV pilin genes (pilEL). An insertion mutation was constructed in pilEL and introduced into the L. pneumophila wild-type strain by allelic exchange. The pilin mutant is defective for expression of long pili. Reintroduction of the pilin locus on a cosmid vector restores expression of the long pili. The L. pneumophila pilEL mutant exhibited approximately a 50% decrease in adherence to human epithelial cells (HeLa and WI-26 cells), macrophages (U937 cells), and Acanthamoeba polyphaga but had a wild-type phenotype for intracellular replication within these cells. Southern hybridization analysis showed that the pilEL locus is present in L. pneumophila serogroups 1 through 13 but is variable in 16 other Legionella species. The presence of a type IV pilin gene and its expression by L. pneumophila may provide an advantage for colonization of lung tissues during Legionnaires' disease and invasion of amoebas in the environment.

Transcriptional regulation of the macrophage-induced gene (gspA) of Legionella pneumophila and phenotypic characterization of a null mutant

Expression of the global stress protein gene (gspA) is induced during the intracellular infection of macrophages and upon exposure of Legionella pneumophila to in vitro stress stimuli. Transcription of gspA is regulated by two promoters, one of which is regulated by the sigma 32 heat-shock transcription factor. We utilized a gspA promoter fusion to a promoter less lacZ to probe the phagososmal 'microenvironment' for the kinetics of exposure of intracellular L. pneumophila to stress stimuli. Expression through the gspA promoter was constitutively induced by approx. 16-fold throughout the intracellular infection, and occurred predominantly through the sigma 32-regulated promoter. Expression of the gspA promoter was induced approx. 4.5-fold, 5-, 11- and 9-fold upon exposure of L. pneumophila to heat shock, oxidative stress, acid shock, and osmotic shock, respectively. An isogenic insertion mutant of L. pneumophila in gspA (strain AA224) was constructed by allelic exchange in the wild-type strain AA200. Compared to in vitro-grown wild-type strain AA200, AA224 was more susceptible to all four in vitro stress stimuli. The wild-type phenotypes were restored to strain AA224 by complementation with a plasmid containing wild-type gspA. There was no difference between the wild-type strain and the gspA mutant in cytopathogenicity to U937 cells or in their kinetics of intracellular replication within macrophages and amoebae. However, compared to in vitro-grown bacteria, macrophage-grown and amoebae-grown AA200 and AA224 showed an equal and dramatic increase in resistance to in vitro stress stimuli. Our data showed that regardless of the capacity of L. pneumophila to subvert the microbicidal mechanisms of the macrophage, intracellular L. pneumophila is exposed to a high level of stress stimuli throughout the intracellular infection. Although the GspA protein is required for protection of the bacteria against in vitro stress stimuli, and is induced during intracellular multiplication, the loss of its function is probably compensated for by other macrophage-induced and stress-induced proteins within the intracellular environment.

Cancer risks among iron and steel workers in Anshan, China, Part I: Proportional mortality ratio analysis

A standardized proportional mortality ratio (SPMR) study of 8,887 deaths during 1980-1989 among male workers in a large integrated iron-steel complex in Anshan, China, was conducted to provide clues to occupational risk factors. Accidents and cancer accounted for a higher proportion of deaths among the iron-steel workers than among the general male population (SPMR = 1.21; 95% CI = 1.12-1.31 and 1.14; 95% CI = 1.10-1.18, respectively). Among all workers, SPMRs were significantly elevated for stomach, lung, and colorectal cancers (SPMR = 1.37, 1.37, 1.38, respectively), but not other cancers. Risks of stomach cancer appeared to be highest among workers employed in jobs with exposure to iron and coal dust, whereas significant increases in colorectal cancer were seen for loading and other dusty jobs and for administrative and sedentary jobs without dust exposure. Risks of lung cancer appeared increased for a variety of jobs throughout the complex, especially those with probable high levels of exposure to polycyclic hydrocarbons and asbestos. Risk of esophageal cancer was significantly elevated for fire-resistant brick makers, and risk of nonmalignant respiratory disease was significantly elevated for those employed as furnace workers, foundry workers, and fire-resistant brick makers.

Cancer risks among iron and steel workers in Anshan, China, Part II: Case-control studies of lung and stomach cancer

Nested case-control interview studies of lung cancer (610 incident cases), stomach cancer (292 incident cases), and 959 controls were conducted to follow up leads from a proportional mortality analysis of deaths among male workers in a large integrated iron-steel complex in Anshan, China. For lung cancer, after adjusting for the significant non-occupational risk factors (smoking, other pulmonary disease, family history of lung cancer, and low consumption of fruit or tea), risks were significantly elevated for those employed for 15 or more years in smelting and rolling (OR = 1.5, CI = 1.1-2.2), in the fire-resistant brick factory (OR = 2.9, CI = 1.4-5.9), in general loading (OR = 2.5, CI = 1.0-6.1), and as coke oven workers (OR = 3.4; CI = 1.4-8.5). For stomach cancer, after adjusting for consumption of pickled vegetables, prior gastric diseases, family history of stomach cancer, low intake of fruits and vegetables, and education, risks were significantly elevated for those employed for 15 or more years in ore sintering and transportation (OR = 2.1, CI = 1.0-4.4), in the fire-resistant brick factory (OR = 2.5, CI = 1.1-5.8), in general loading (OR = 3.2, CI = 1.2-8.9), as boilerworkers and cooks (OR = 2.6, CI = 1.2-5.6), and as coke oven workers (OR = 5.4, CI = 1.8-16.0). For both lung and stomach cancers, significant dose-response gradients were observed for exposure to total dust and benzo(a)pyrene, but not for specific chemical components of dust. Overall, long-term steel workers with exposure to workplace pollutants had a 40% increased risk of both lung and stomach cancers. These case-control studies confirm many of the occupational findings reported in the proportionate mortality analysis, and suggest avenues for further work to evaluate the carcinogenicity of individual components of dust.

Learning disabilities and learned helplessness: a heuristic approach

This study investigated whether students with learning disabilities exhibited learned helpless behavior at a greater rate than their normal achieving peers when confronted with reading failure. Forty-five third grade students from a suburban elementary schools were participants in the study. Thirty of the subjects were classified as having a learning disability (LD) and the remaining 15 subjects were from regular education (RE) classrooms. Fifteen of the students with LD were placed in the treatment group and the remaining fifteen were placed in the control group. All the regular education students were placed in the treatment group. After randomly assigning the students with LD into either a treatment (stressed) group or a control (nonstressed) group, the stressed students were administered a reading instrument in order to measure how they dealt with failure. A one-way ANCOVA was conducted to determine whether significant differences existed between the groups based on their posttest scores. The results indicate that stressed students with LD have a significantly more difficult time recovering from stress than their regular education peers.

Occupational risks for cutaneous melanoma among men in Sweden

A population-based linked-registry was used to evaluate incidence of malignant melanoma of the skin among Swedish men by industry and occupation. There were 3850 cutaneous melanoma cases identified in the 19-year follow-up of men employed in 1960. New associations were observed for men employed in the breweries and malt-processing industry and in shoe fabrication from leather and skins. Several findings supported associations previously reported in other countries, including an excess risk among workers in basic chemical production and the printing industry and among professional, technical, and white-collar workers. Risk overall was not increased among farmers, despite a significant excess of melanoma of the face, neck, and scalp. Although this linked registry analysis lacked information about specific agents, duration of employment, and occupational and recreational sun exposures, it did provide leads for new associations and confirmed previous ones. Nevertheless, because of these limitations, etiologic clues must be interpreted cautiously.

Salmonella enteritidis has a homologue of tolC that is required for virulence in BALB/c mice

The ability of Salmonella to invade tissue culture cells is correlated with virulence. Therefore, the tissue culture invasion model has been used extensively to study this process and to identify the bacterial genes involved and their products. Described here is the further characterization of a Salmonella enteritidis mutant (SM6T) originally identified as a non-invasive for tissue culture cells. A chromosomal DNA fragment complementing this defect was cloned and sequenced. The derived protein sequence is 89% identical to TolC from Escherichia coli, an outer membrane protein required for the signal peptide-independent transport of alpha-haemolysin and colicin V. Therefore, sinA was renamed tolC and is referred to in this text as tolCs to distinguish it from tolC of E. coli. TolCs and TolC are functionally similar since tolC can complement the invasion-defective phenotype of a tolCs mutant, and tolCs is required for export of alpha-haemolysin by Salmonella. The tolCs mutant is avirulent for mice when administered by the oral route, suggesting that the gene is important for virulence. Further characterization of the tolCs mutant indicated that like tolC mutants it is more sensitive than the wild-type strain to various detergents, antibiotics and dyes. This mutant is more sensitive to Triton X-100 only when associated with the monolayer, and the invasion-defective phenotype appears to be artifact of this sensitivity. In addition, the tolCs mutant is more sensitive to the bactericidal activity of human serum. Therefore, the avirulent phenotype could be the result of an inability to secrete a necessary virulence factor, or an increased sensitivity to complement and detergents as a result of a subtle alteration in the lipopolysaccharide (LPS) associated with tolC mutations.

Esophageal cancer and occupation in a cohort of Swedish men

Using the Cancer Environment Registry of Sweden, which links the 1960 census information on employment with cancer incidence data from 1961-1979, we conducted a systematic, population-based assessment of esophageal cancer incidence by industry and occupation for men in Sweden. A general reduction in esophageal cancer incidence was found among agricultural and professional workers, whereas excess incidence was found among business, sales, and some craftsmen and production jobs. Elevated incidence was associated with several specific industries, including the food (SIR = 1.3, p < 0.05), beverage and tobacco (SIR = 1.8, p < 0.05) industries, vulcanizing shops within the rubber industry (SIR = 4.7, p < 0.01), and certain automotive building industries. Incidence also was increased among brewery workers (SIR = 4.2, p < 0.01) and butchers (SIR = 2.1, p < 0.01), and among individuals with certain service jobs, particularly waiters in the hotel and restaurant industry (SIR = 3.1, p < 0.01). Some of the occupational associations may be explained by lifestyle factors such as alcohol drinking and smoking, whereas others are specific and tend to support those of earlier investigations. This study adds to the evidence of a small but possibly important role of occupation in esophageal cancer etiology.

Recent cancer trends in the United States

BACKGROUND

Cancer incidence rates have been reported to be increasing in the United States, although trends vary according to form of cancer.

PURPOSE

We identify the cancers accounting for the rising incidence, quantify the changes that have occurred from the mid-1970s to the early 1990s, and contrast incidence and mortality trends to provide clues to the determinants of the temporal patterns.

METHODS

Sex-, race-, and age-specific and age-adjusted incidence rates for the 5-year periods 1987-1991 versus 1975-1979 were calculated for 28 cancers among men and 30 cancers among women using data from the Surveillance, Epidemiology, and End Results (SEER) Program of cancer registration covering about 10% of the U.S. population. Similar rates were computed using national mortality data. Cancers were ranked according to the change in incidence rates over the two periods.

RESULTS

Age-adjusted incidence rates for all cancers combined increased by 18.6% among males and 12.4% among females from 1975-1979 to 1987-1991, due largely to rising rates for prostate cancer among men and for breast and lung cancers among women. National mortality rates for all cancers combined rose less steeply, 3% and 6% among men and women, respectively, driven mostly by continuing increases in lung cancer mortality, while death rates for the majority of the cancers were steady or declining. Total cancer incidence rose at all ages, but with different tumors responsible for the increases at different ages: leukemia and brain/nervous system cancer among children; testicular cancer, nonmelanoma skin cancer (largely Kaposi's sarcoma), non-Hodgkin's lymphoma, and melanoma among young and middle-aged adults; and prostate, breast, and lung cancers among older individuals. In contrast, mortality rates for all cancers combined declined among both males and females under age 55 years, increasing only among older persons.

CONCLUSIONS

Trends in cancer incidence and mortality differ. For most cancers, incidence rates are rising, while mortality rates are generally stable or declining.

IMPLICATIONS

Much of the recent increase in cancer incidence can be explained by known factors. Improved detection appears to account for most of the increases in breast cancer among women and prostate cancer among men. On the other hand, cigarette smoking is the major determinant of the rise in lung cancer among women, acquired immunodeficiency syndrome has led to increases in non-Hodgkin's lymphoma and Kaposi's sarcoma among young and middle-aged men, and sunlight exposure patterns have affected the trends in melanoma. Some trends remain unexplained, however, and may reflect changing exposures to carcinogens yet to be identified and clarified.

Occupation and hematopoietic and lymphoproliferative malignancies among women: a linked registry study

Using a nationwide linked registry, we evaluated the incidence of several hematopoietic and lymphoproliferative (HLP) malignancies among Swedish women from 1961 to 1979 by industry and occupation. The risks of one or more types of HLP cancers (including the leukemias, non-Hodgkin's lymphoma, multiple myeloma, and mycosis fungoides) were significantly increased among women working in the agriculture and textile industries, housekeepers, and post office employees. Limitations of these linked-registry data include lack of detailed information on specific exposures and duration of employment, and the relatively small sizes of specific occupational cohorts. Nevertheless, as the proportion of women entering the workforce continues to increase, this data resource may provide additional clues to occupational determinants of HLP and other malignancies.

Mouse T lymphocytes that express a gamma delta T-cell antigen receptor contribute to resistance to Salmonella infection in vivo

Mice depleted of lymphocytes expressing the alpha beta or the gamma delta T-cell receptor for antigen (TCR) by antibody treatment were infected orally with Salmonella enteritidis. In both groups of treated mice, the 50% lethal dose decreased, suggesting that both the alpha beta TCR+ and the gamma delta TCR+ subsets contribute to resistance to oral infection. These data provide further evidence for the contribution of gamma delta T cells in the response to bacterial infections.

Occupation and stomach cancer in a cohort of Swedish men

Using the Cancer-Environment Registry of Sweden, which links the 1960 census information on employment with cancer incidence data from 1961-1979, we conducted a systematic, population-based assessment of stomach cancer incidence by industry and occupation for men in Sweden. Nearly 17,000 stomach cancer cases were diagnosed during the 19 years of follow-up. Stomach cancer incidence was elevated among miners and quarrymen, farmers and fishermen, and craftsmen and production workers. Men who held white collar jobs, including professional and technical, administrative and management, clerical, and sales jobs, had a reduction in stomach cancer incidence. Examination of specific jobs revealed generally elevated rates of stomach cancer among men who may be exposed to dusty work environments, such as quarry workers, stone cutters, circular and plane operators, construction workers, crane operators, heavy laborers, and shop and construction metal workers. These occupational associations mostly were observed for stomach cancers of noncardia origin, and no significant associations were found with cardia cancers. We had no information on dietary or other potential confounding factors and cannot make inferences about the role of occupation per se, but the current findings support those of earlier investigations and add to the evidence of a small but significant occupational role in stomach carcinogenesis.

Occupational risks for colon cancer in Sweden

Using the Cancer-Environment Registry of Sweden, which links census information (1960) with cancer incidence data (1961 to 1979), we conducted a systematic, population-based assessment of colon cancer incidence among cohorts defined by industry and occupation for all employed persons in Sweden. Small but statistically significant excesses of colon cancer were observed among white-collar occupations, including administrators, professionals, and clerical and sales workers, whereas a reduction in incidence was found among workers in agricultural and related jobs, such as farmers, fishermen, and hunters. Analysis by subsite within the colon revealed little difference in results. The observed risk patterns are consistent with previous reports on colon cancer risk and occupational physical activity levels, ie, elevated risk among sedentary white-collar workers and reduced risk among agricultural workers. Few craftsman and production processing jobs were linked to colon cancer, although statistically significant excesses were observed among shoe and leather workers, metal smiths, and foundry workers in the metal manufacturing industry. The findings indicate that occupation in general is likely to play a relatively small role in colon cancer etiology, with perhaps its major contribution an indirect one via physical activity.

Occupation and lung cancer risk among women in northern China

Lifetime occupational histories were obtained in a case-control study of 965 female lung cancer patients and 959 controls selected from the general population in Shenyang and Harbin, People's Republic of China, where most women have worked outside the home. After adjusting for smoking, we found a significantly increased risk of lung cancer associated with employment involving the manufacture of transportation equipment (OR = 1.6, 95% CI = 1.0, 2.6), in particular the manufacturing of automobiles (OR = 3.0, 95% CI = 1.4, 6.4). Metal smelting and treatment workers were at an increased risk of lung cancer (OR = 1.5, 95% CI = 1.0, 2.1); the highest risks were observed among metal surfacers (OR = 3.1, 95% CI = 1.1, 9.0) and currently employed foundry workers (OR = 13.0, 95% CI = 1.7, 99.4). On the other hand, about a 50% decreased risk of lung cancer was observed among those employed in textile industries or as leaders of state and party organizations. Based on self-reports, exposures to coal dust and smoke from burning fuel at the workplace were also significant risk factors. The findings were similar when the analyses were confined to nonsmokers and were comparable across the major cell types of lung cancer.

Bias in learning disabilities placement

A nationally representative sample of 20,614 eighth grade students was examined for bias in placement decisions for children said to have learning disabilities. Factors investigated for bias were race, sex, and socioeconomic status. Path analysis showed significant and direct paths from sex and race to placement, controlling for socioeconomic status, academic ability, and behavioral competency. Boys were overrepresented in such classes beyond what their somewhat lower academic and behavioral competencies would predict. Caucasians were similarly overrepresented controlling for other variables in the model. It appears that boys and Caucasians are overrepresented in learning disabilities placements on a national scale even when other contributing factors are controlled.

Identification of novel loci affecting entry of Salmonella enteritidis into eukaryotic cells

There are an estimated 2 million cases of salmonellosis in the United States every year. Unlike the incidence of many infectious diseases, the incidence of salmonellosis in the United States and other developed countries has been rising steadily over the past 30 years, and the disease now accounts for 10 to 15% of all cases of acute gastroenteritis in the United States. The infecting organism is ingested and must traverse the intestinal epithelium to reach its preferred site for multiplication, the reticuloendothelial system. Despite several recent studies, the genetic basis of the invasion process is poorly understood. An emerging theme from these studies is that wild-type Salmonella organisms probably have several chromosomal loci that are required for the most efficient level of invasion. In this study, we have identified and characterized 13 TnphoA insertion mutants of Salmonella enteritidis CDC5 that exhibit altered invasion phenotypes. The mutants were identified by screening a bank of TnphoA insertions in S. enteritidis CDC5str for their invasion phenotype in three tissue culture cell lines (HEp-2, CHO, and MDCK). These 13 mutants were separated into six classes based on their invasive phenotypes in the tissue culture cell lines. Several mutants were defective for entry of some cell lines but not for others, while two mutants (SM6 and SM7) were defective for entry into all three tissue culture cell lines. This suggests that Salmonella spp. may express more than one invasion pathway. Southern analysis and chromosomal mapping indicated that as many as nine chromosomal loci may contribute to the invasion phenotype. It is becoming clear that the invasive phenotype of Salmonella spp. is multifactorial and more complex than that of some other invasive members of the family Enterobacteriaceae.

Mortality among dust-exposed Chinese mine and pottery workers

A cohort study of approximately 68,000 persons employed during 1972 to 1974 at metal mines and pottery factories in south central China was conducted to evaluate mortality from cancer and other diseases among workers exposed to different levels of silica and other dusts. A follow-up of subjects through December 31, 1989 revealed 6,192 deaths, a number close to that expected based on Chinese national mortality rates. There was, however, a nearly 6-fold increase in deaths from pulmonary heart disease (standard mortality ratio, 581; 95% confidence interval 538 to 626), and a 48% excess of mortality from nonmalignant respiratory diseases (standard mortality ratio, 148; 95% confidence interval, 139 to 158), primarily because of a more than 30-fold excess of pneumoconiosis. Pulmonary heart disease and noncancerous respiratory disease rates rose in proportion to dust exposure. Cancer mortality overall was not increased among the miners or pottery workers. There was no increased risk of lung cancer, except among tin miners, and trends in risk of this cancer with increasing level of dust exposure were not significant. Risks of lung cancer were 22% higher among workers with than without silicosis. The findings indicate that respiratory disease continues to be an occupational hazard among Chinese miners and pottery workers, but that cancer risks are not as yet strongly associated with work in these dusty trades.

Renal cell cancer among architects and allied professionals in Sweden

The Swedish Cancer-Environment Registry was used to evaluate a recent report of a large excess risk of renal cell cancer among architects in Los Angeles. We identified 131 renal cell cancers among male Swedish architects and allied professionals during a 19-year follow-up period (1961-1979). Compared with the Swedish population, there was no significant excess of renal cell cancer among architects and allied professionals (standardized incidence ratio (SIR) = 1.15; 131 cases). Although it was not possible to estimate the risk for architects alone, the SIR was only 1.06 (16 cases) in a subset of professionals employed in architectural and engineering firms. However, a significant increase in risk (SIR = 1.38) was observed in a related group of workers employed as engineers and construction supervisors in the home construction industry.

Incidence of childhood cancer in twins

The incidence of childhood cancer in twins was evaluated by linking a roster of 30,925 twins born in Connecticut (United States) between 1930 and 1969 with the Connecticut Tumor Registry. Cancer, exclusive of nonmelanoma skin cancer, was identified in 19 females and 12 males under 15 years of age. The incidence rate among twins was 7.9 cancers per 100,000 person-years (PY) overall, and 9.7 and 6.1 per 100,000 PYs for females and males, respectively. Four of 13 leukemias occurred in two female twin pairs, representing concordance rates of 18 percent overall and 29 percent for like-sex pairs, which are somewhat higher than values reported previously. The number of cancers expected was computed on the assumption that twins experienced the same sex-, age-, and calendar time-specific cancer rates as recorded for all Connecticut-born children. Because active follow-up of individuals was not conducted, an adjustment to person-years of observation was made to account for childhood mortality, including the high perinatal mortality characteristic of twins. Childhood cancer was 30 percent less frequent than expected (standardized incidence ratio [SIR] = 0.7; 95 percent confidence interval [CI] = 0.5-0.9), a deficit that is marginally greater than those found in previous studies. Both leukemia (SIR = 0.8; CI = 0.4-1.4), and all other cancers combined (SIR = 0.6; CI = 0.3-0.9) occurred less often than expected. The deficit was greater among males (SIR = 0.5; CI = 0.2-0.8) than among females (SIR = 0.9; CI = 0.5-1.4) and was especially pronounced among males younger than five years (SIR = 0.2; CI = 0.0-0.7). The data support the view that twins, particularly male twins, have a lower risk of childhood cancer than single-born children. Any added risk for twins associated with their greater frequency of exposure to prenatal X-rays appears to have been insufficient to offset an 'effect' of twinning per se. Possible explanations for this finding include (i) the low birthweight distribution of twins, or (ii) selective early mortality of twin fetuses or neonates who would otherwise have developed a clinical cancer.

Therapeutic radiation at a young age is linked to secondary thyroid cancer. The Late Effects Study Group

We estimated the risk of thyroid cancer among 9170 patients who had survived 2 or more years after the diagnosis of a cancer in childhood. As compared with the general population, patients had a 53-fold increased risk (95% confidence interval, 34-80). Risk increased significantly with time since treatment for the initial cancer (P = 0.03). Detailed treatment data were obtained for 23 cases and 89 matched controls from the childhood cancer cohort. Sixty-eight % of the thyroid cancers arose within the field of radiation. Radiation doses to the thyroid of greater than 200 cGy were associated with a 13-fold increased risk (95% confidence interval, 1.7-104). The risk of thyroid cancer rose with increasing dose (P less than 0.001), but this was derived almost entirely from the increase from less than 200 to greater than 200 cGy. The risk of thyroid cancer did not decrease, however, at radiation doses as high as 6000 cGy.

Correlates of liver cancer mortality in China

To provide clues to the causes of liver cancer in China, we studied the correlation of certain dietary and biochemical markers with liver cancer mortality across 65 Chinese counties. Mortality rates were significantly linked to the county-wide prevalence of hepatitis-B surface antigen positivity. Rates were also higher in counties with high plasma levels of total cholesterol and high consumption of liquor, rapeseed oil, and mouldy corn, while inverse associations were observed for wheat consumption. All of the observed associations, except those with cholesterol and rapeseed oil, were more pronounced in men than in women. No significant correlations with liver cancer mortality were found for consumption of several other foods; plasma levels of retinol, beta-carotene, alpha-tocopherol, selenium, zinc and ferritin; or urine levels of aflatoxin B1. Although causal inferences cannot be derived, this ecological study suggests that chronic infection with hepatitis-B virus contributes to the substantial variation in liver cancer mortality in China, and provides leads for further studies into the role of dietary and nutritional determinants.

Lung cancer among women in north-east China

A case-control study of lung cancer involving interviews with 965 female patients and 959 controls in Shenyang and Harbin, two industrial cities which have among the highest rates of lung cancer in China, revealed that cigarette smoking is the main causal factor and accounted for about 35% of the tumours among women. Although the amount smoked was low (the cases averaged eight cigarettes per day), the percentage of smokers among women over age 50 in these cities was nearly double the national average. Air pollution from coal burning stoves was implicated, as risks of lung cancer increased in proportion to years of exposure to 'Kang' and other heating devices indigenous to the region. In addition, the number of meals cooked by deep frying and the frequency of smokiness during cooking were associated with risk of lung cancer. More cases than controls reported workplace exposures to coal dust and to smoke from burning fuel. Elevated risks were observed for smelter workers and decreased risks for textile workers. Prior chronic bronchitis/emphysema, pneumonia, and recent tuberculosis contributed significantly to lung cancer risk, as did a history of tuberculosis and lung cancer in family members. Higher intake of carotene-rich vegetables was not protective against lung cancer in this population. The findings were qualitatively similar across the major cell types of lung cancer, except that the associations with smoking and previous lung diseases were stronger for squamous/oat cell cancers than for adenocarcinoma of the lung.

Indoor radon and lung cancer in China

Radon has long been known to contribute to risk of lung cancer, especially in undergound miners who are exposed to large amounts of the carcinogen. Recently, however, lower amounts of radon present in living areas have been suggested as an important cause of lung cancer. In an effort to clarify the relationship of low amounts of radon with lung cancer risk, we placed alpha-track radon detectors in the homes of 308 women with newly diagnosed lung cancer and 356 randomly selected female control subjects of similar age. Measurements were taken after 1 year. All study participants were part of the general population of Shenyang, People's Republic of China, an industrial city in the northeast part of the country that has one of the world's highest rates of lung cancer in women. The median time of residence in the homes was 24 years. The median household radon level was 2.3 pCi/L of air; 20% of the levels were greater than 4 pCi/L. Radon levels tended to be higher in single-story houses or on the first floor of multiple-story dwellings, and they were also higher in houses with increased levels of indoor air pollution from coal-burning stoves. However, the levels were not higher in homes of women who developed lung cancer than in homes of controls, nor did lung cancer risk increase with increasing radon level. No association between radon and lung cancer was observed regardless of cigarette-smoking status, except for a nonsignificant trend among heavy smokers. No positive associations of lung cancer cell type with radon were observed, except for a nonsignificant excess risk of small cell cancers among the more heavily exposed residents. Our data suggest that projections from surveys of miners exposed to high radon levels may have overestimated the overall risks of lung cancer associated with levels typically seen in homes in this Chinese city. However, further studies in other population groups are needed to clarify the carcinogenic potential of indoor radon.

Smoking, air pollution, and the high rates of lung cancer in Shenyang, China

A case-control study involving interviews with 1,249 patients with lung cancer and 1,345 population-based controls was conducted in Shenyang, an industrial city in northeastern China, where mortality rates are high among men and women. Cigarette smoking was found to be the principal cause of lung cancer in this population, accounting for 55% of the lung cancers in males and 37% in females. The attributable risk percentage among females is high compared to elsewhere in China, largely because of a higher prevalence of smoking among women. After adjustment for smoking, there were also significant increases in lung cancer risk associated with several measures of exposure to air pollutants. Risks were twice as high among those who reported smoky outdoor environments, and increased in proportion to years of sleeping on beds heated by coal-burning stoves (kang), and to an overall index of indoor air pollution. Threefold increases in lung cancer risk were found among men who worked in the nonferrous smelting industry, where heavy exposures to inorganic arsenic have been reported. The associations with both smoking and indoor air pollution were stronger for squamous cell and small cell carcinomas than for adenocarcinoma of the lung. Risks due to smoking or air pollution were not greatly altered by adjustment for consumption of fresh vegetables or sources of beta carotene or retinol, prior chronic lung diseases, or education level. The findings suggest that smoking and environmental pollution combine to account for the elevated rates of lung cancer mortality in Shenyang.

The Danish case-control study of cutaneous malignant melanoma. III. Hormonal and reproductive factors in women

The relationship between cutaneous malignant melanoma in women and reproductive and hormonal factors was investigated in a population-based case-control study including a total of 280 cases and 536 controls from East Denmark. Patients with lentigo maligna melanoma were not included. No association was found between risk of melanoma and age at menarche, duration of menstrual life, age at natural menopause, age at first pregnancy, or number of pregnancies, live births or miscarriages. There was no evidence of an association between melanoma and use, duration of use or type of oral contraceptives. The use of menopausal replacement therapy was not a risk factor for melanoma. There was no difference in risk associated with hormonal factors between superficial spreading melanoma and nodular melanoma. Our findings suggest that neither reproductive nor hormonal factors increase the risk of melanoma in women in Denmark.

The Danish case-control study of cutaneous malignant melanoma. IV. No association with nutritional factors, alcohol, smoking or hair dyes

In a population-based case-control study from East Denmark including 474 cases with cutaneous malignant melanoma and 926 controls we evaluated the influence of diet, alcohol, smoking, bathing habits and hair dyes on the risk of this cancer. Patients with lentigo maligna melanoma were not included. We observed no effect of dietary factors on risk of melanoma. No association was found between risk of melanoma and alcohol intake, tobacco smoking, bathing habits or hair dye use.

The Danish case-control study of cutaneous malignant melanoma. II. Importance of UV-light exposure

A population-based case-control study of 474 patients with cutaneous malignant melanoma and 926 population controls, conducted in East Denmark over a 3-year period, included an evaluation of the relationship of UV-light exposure to cutaneous melanoma risk. Patients with lentigo maligna melanoma were not included. Significantly increased risk was associated with severe sunburn before age 15 (RR = 2.7 for 5 + vs. never), sunbathing (RR = 1.6), boating (RR = 1.4) and vacations spent in the sun (RR = 1.4 for very sunny vs. never). A significant decrease in risk was associated with occupational exposure during the summer in males (RR = 0.7), and no association with cutaneous microtopography was seen. These findings were independent of the effects of constitutional risk factors (naevi, freckles and light hair colour). No association was found between the risk of cutaneous melanoma and exposure to artificial UV-light (fluorescent light, sun lamps, or sun beds). No significant difference was found between superficial spreading melanoma and nodular melanoma with regard to any of the sun exposure variables. Our data indicate that exposure to intermittent intense sunlight is an important risk factor for cutaneous malignant melanoma, while long-term continuous exposure does not appear to be risk factor.

Geographic pattern of lung cancer in Japan and its environmental correlations

Standardized lung cancer mortality ratios, 1969-1978, for basic administrative units of Japan were related to various environmental characteristics by multiple regression analysis. Elevated lung cancer mortality was demonstrated in the areas along the sea coast, particularly those with fishing ports, low socioeconomic status, and high level of air pollution. High mortality was also observed in coal mining areas and areas with shipyards. Data on tobacco expenditures provided partial adjustment for the effects of cigarette smoking on these correlations.

The Danish case-control study of cutaneous malignant melanoma. I. Importance of host factors

The relationship between cutaneous malignant melanoma and possible host factors was investigated in a population-based case-control study from East Denmark over a 3-year period. A total of 474 melanoma patients and 926 population controls aged 20-79 years were interviewed. Patients with lentigo maligna melanoma were not included. The major constitutional risk factors were: number of raised naevi on the arms (RR = 5.1 for 5+ vs. none), degree of freckling (RR = 2.9 for many vs. none), and light hair colour (RR = 1.7 for blond/fair vs. dark brown/black), which were independent of one another. An apparent synergy between number of raised naevi on the arms and degree of freckling was found. Thus, persons at high risk of melanoma may be identified by a simple assessment of naevi and degree of freckling. No significant difference was found between superficial spreading melanoma and nodular melanoma with regard to the most important host factors.

An examination of the Wechsler Adult Intelligence Scale (WAIS) subtests from a neuropsychological perspective

Individual subtest scores of the Wechsler Adult Intelligence Scale (WAIS) were regressed on measures of the Halstead-Reitan Neuropsychological Battery (HRNB) for 408 psychiatric and neurologic patients. The results suggested that language skills (Aphasia Screening Test), auditory attention (Seashore Rhythm Test), psychomotor speed and general cognitive functioning (Category Test) were underlying the performance in the majority of WAIS subtests. A canonical correlation was performed to consider the degree of commonality between the WAIS and the HRNB. One significant canonical correlation between the linear components of the WAIS and HRNB tests emerged. Canonical variates showed that Block Design, Digit Symbol, and Similarities subtests of the WAIS overlapped with the Aphasia Screening Test and the Category Test of the HRNB. It was concluded that, while shared variance does exist between the WAIS and the HRNB, each offers nonredundant information regarding neuropsychological functioning.

Multiple myeloma and occupation in Sweden

The occurrence of multiple myeloma by occupational and industrial category was systematically assessed using the Swedish Cancer-Environment Registry, which links cancer incidence (1961-1979) with occupational data from the 1960 census. Incidence of multiple myeloma was significantly increased for a number of occupational groups such as farmers, smelter and metallurgy workers, and miners-quarrymen-rock blasters. Although caution must be applied in drawing causal inferences, this national linked-registry analysis may provide clues to the environmental determinants of multiple myeloma.

Leukemias and occupation in Sweden: a registry-based analysis

A linked-registry was used to examine systematically, on a national basis, the leukemia incidence in Swedish men by industry and occupation. New associations were observed for chronic lymphocytic leukemia among cloth and pattern cutters and for chronic myelocytic leukemia among brewery workers and motor mechanics. A number of additional findings were consistent with previous observations in other countries. Although etiologic inferences are limited when using linked-registry data, this hypothesis-generating study may provide new clues to the occupational determinants of specific forms of leukemia.

Occupational risks for bladder cancer among men in Sweden

With the use of the Swedish Cancer-Environment Registry, census data on employment in 1960 were linked with registry data on bladder cancer during 1961-79. This hypothesis-generating study revealed for the first time associations between bladder cancer and employment in pulp and fiberboard manufacturing, in rope and twine making, and work as a dental technician. Statistically significant increases in risk were also found for several occupations previously associated with bladder cancer, including barbers and beauticians, artistic painters, toolmakers and machinists, and physicians, and employment in butcher shops, industrial chemical making, apparel manufacturing, and plumbing. Etiologic inferences cannot be made from this investigation, but the findings from this large national resource provide further clues to the occupational determinants of bladder cancer.

Bone sarcomas linked to radiotherapy and chemotherapy in children

We estimated the risk of subsequent bone cancer among 9170 patients who had survived two or more years after the diagnosis of a cancer in childhood. As compared with the general population, the patients had a relative risk of 133 (95 percent confidence interval, 98 to 176) and a mean (+/- SE) 20-year cumulative risk of 2.8 +/- 0.7 percent. Detailed data on treatment were obtained on 64 patients in whom bone cancer developed after childhood cancer. As compared with 209 matched controls who had survived cancer in childhood but who did not have bone cancer later, patients who had had radiation therapy had a 2.7-fold risk (95 percent confidence interval, 1.0 to 7.7) and a sharp dose-response gradient reaching a 40-fold risk after doses to the bone of more than 6000 rad. The relative dose-response effect among patients who had been treated for retinoblastoma resembled that among patients with all other types of initial tumors, although the cumulative risk of bone cancer in the retinoblastoma group was higher. Similar numbers of patients were treated with orthovoltage and megavoltage; the patterns of risk among categories of doses did not differ according to the type of voltage. After adjustment for radiation therapy, treatment with alkylating agents was also linked to bone cancer (relative risk, 4.7; 95 percent confidence interval, 1.0 to 22.3), with the risk increasing as cumulative drug exposure rose. We conclude that both radiotherapy and chemotherapy with alkylating agents for childhood cancer increase the subsequent risk of bone cancer.

Leukemia after therapy with alkylating agents for childhood cancer

The risk of leukemia was evaluated in 9,170 2-or-more-year survivors of childhood cancer in the 13 institutions of the Late Effects Study Group. Secondary leukemia occurred in 22 nonreferred individuals compared to 1.52 expected, based on general population rates [relative risk (RR) = 14; 95% confidence interval (CI), 9-22]. The influence of therapy for the first cancer on subsequent leukemia risk was determined by a case-control study conducted on 25 cases and 90 matched controls. Treatment with alkylating agents was associated with a significantly elevated risk of leukemia (RR = 4.8; 95% CI, 1.2-18.9). A strong dose-response relationship was also observed between leukemia risk and total dose of alkylating agents, estimated by an alkylator score. The RR of leukemia reached 23 in the highest dose category. Radiation therapy, however, did not increase risk. Although doxorubicin was also identified as a possible risk factor, the excess risk of leukemia following treatment for childhood cancer appears almost entirely due to alkylating agents.

Occupational risks for renal cancer in Sweden

A systematic assessment was made of the occurrence of renal cancer among men by industrial and occupational classification using the Cancer-Environment Registry, which links cancer incidence (1961-79) and census data (1960) with industry and occupation for all employed individuals in Sweden. Data were analysed separately for cancers of the renal parenchyma and pelvis. Significantly increased risks for renal cell cancer were observed for several professional and white collar occupations, including physicians and others in the health care industry. By contrast, the risks for renal pelvis cancer tended to be higher among blue collar workers, especially in the machine industry. Deficits of both cancers occurred among farmers. The findings of the survey are considered as aetiological clues that may deserve further study, although some associations support observations in other countries.