Most acute myeloid leukemia progenitor cells with long-term proliferative ability in vitro and in vivo have the phenotype CD34(+)/CD71(-)/HLA-DR-

Acute myeloid leukemia (AML) occurs as the result of malignant transformation in a hematopoietic progenitor cell, which proliferates to form an accumulation of AML blasts. Only a minority of these AML cells are capable of proliferation in vitro, suggesting that AML cells may be organized in a hierarchy, with only the most primitive of these cells capable of maintaining the leukemic clone. To further investigate this hypothesis, we have evaluated a strategy for purifying these primitive cells based on surface antigen expression. As an in vitro endpoint, we have determined the phenotype of AML progenitor cells which are capable of producing AML colony-forming cells (CFU) for up to 8 weeks in suspension culture (SC) and compared the phenotype with that of cells which reproduce AML in nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice. AML cells were fluorescence-activated cell sorted (FACS) for coexpression of CD34 and CD71, CD38, and/or HLA-DR and the subfractions were assayed in vitro and in vivo at various cell doses to estimate purification. While the majority of primary AML CFU lacked expression of CD34, most cells capable of producing CFU after 2 to 8 weeks in SC were CD34(+)/CD71(-). HLA-DR expression was heterogeneous on cells producing CFU after 2 to 4 weeks. However, after 6 to 8 weeks in SC, the majority of CFU were derived from CD34(+)/HLA-DR- cells. Similarly, the majority of cells capable of long-term CFU production from SC were CD34(+)/CD38(-). Most cells that were capable of engrafting NOD/SCID mice were also CD34(+)/CD71(-) and CD34(+)/HLA-DR-. Engraftment was not achieved with CD34(+)/CD71(+) or HLA-DR+ subfractions, however, in two patients, both the CD34(+) and CD34(-) subfractions were capable of engrafting the NOD/SCID mice. A three-color sorting strategy combining these antigens allowed approximately a 2-log purification of these NOD/SCID leukemia initiating cells, with engraftment achieved using as few as 400 cells in one experiment. Phenotyping studies suggest even higher purification could be achieved by combining lack of CD38 expression with the CD34(+)/CD71(-) or CD34(+)/HLA DR- phenotype. These results suggest that most AML cells capable of long-term proliferation in vitro and in vivo share the CD34(+)/CD71(-)/HLA-DR- phenotype with normal stem cells. Our data suggests that in this group of patients the leukemic transformation has occurred in a primitive progenitor, as defined by phenotype, with some degree of subsequent differentiation as defined by functional assays.

Use of a life events calendar approach to elicit occupational history from farmers

BACKGROUND

Precise and valid exposure assessment is generally the primary challenge in retrospective occupational epidemiology studies, particularly when the only available method for exposure characterization is a personal interview. Agricultural workers may represent a particular challenge; for example, whereas many farmers have worked from childhood at the same location, raising the same crops and animals, they may have used different equipment, chemicals, and protective gear over time. One method to assist in recall is the "life events calendar," a cognitive tool based on the subject's own life history to help anchor occupational activities in time.

METHODS

Unstructured interviews of farmers, focus groups, and pilot interviews among rural men, primarily African-Americans, were conducted to create a questionnaire for obtaining farm history information within the context of personal life events.

RESULTS

Farmers used both personal events and national events (as well as events relating directly to farming) to recall their activities. These subjects had extensive history of farming (10-75 years) and chemical use (median lifetime chemicals = 13).

CONCLUSION

The life events calendar provided a useful tool to facilitate the recall of a lifetime of agricultural activity. Life events calendars are useful additions to the tools available for retrospective occupational exposure assessment.

Risk for prostate cancer by occupation and industry: a 24-state death certificate study

Current knowledge of the etiology of prostate cancer is limited. Numerous studies have suggested that certain occupations and industries may be associated with the occurrence of prostate cancer. Information on occupation and industry on death certificates from 24 states gathered from 1984 to 1993 was used in case control study on prostate cancer. A total of 60,878 men with prostate cancer as underlying cause of death was selected and matched with controls who died of all other causes except cancer. Similar to the findings of our parallel large case control study of prostate cancer, we observed excess risks in some white-collar occupations, such as administrators, managers, teachers, engineers, and sales occupations. However, some blue-collar occupations, such as power plant operators and stationary engineers, brickmasons, machinery maintenance workers, airplane pilots, longshoreman, railroad industry workers, and other occupations with potential exposure to PAH also showed risk of excess prostate cancer. Risk was significantly decreased for blue-collar occupations, including farm workers, commercial fishermen, mechanics and repairers, structural metal workers, mining, printing, winding, dry cleaning, textile machine operators, cooks, bakers, and bartenders. Although we observed excess risks of prostate cancer among some low socioeconomic status (SES) occupations, the overall results suggest that the effects of higher SES cannot be ruled out in associations between occupational factors and the risk of prostate cancer.

The proliferative status of haematopoietic progenitor cells in the developing murine liver and adult bone marrow

A class of primitive progenitor cells with high proliferative potential in vitro (HPP-CFC), has been identified in fetal liver and adult bone marrow both in murine and human systems. The kinetic properties of HPP-CFC2 and the more mature granulocyte-macrophage colony forming units (CFU-GM) derived from murine fetal liver on d13, d15 and d19 of gestation, newborn liver and neonatal liver on d3 and d8 postpartum have been evaluated and compared with the kinetic properties of these progenitor cell populations derived from adult bone marrow. The frequency of HPP-CFC2 in fetal liver was found to be greatest on d15 of gestation then subsequently declined in newborn and neonatal liver. Similarly, the highest proportion of HPP-CFC2 engaged in DNA synthesis (53+/-3%) was detected in d15 fetal liver. This proportion decreased to 13+/-2% in the liver 1 wk after birth, which is comparable to the number of HPP-CFC2 derived from adult BM which were in S-phase (10+/-1%). Production of CFU-GM was found to be greater in adult bone marrow than in either fetal or newborn liver. While the proportion of CFU-GM in S-phase was high all 3 tissue samples, the greatest proportion of cycling CFU-GM (50+/-2%) was detected in d15 fetal liver. These results suggest that HPP-CFC2 derived from fetal liver are actively cycling while HPP-CFC2 derived from adult bone marrow are relatively quiescent. In contrast, a high proportion of CFU-GM derived from fetal, newborn liver and adult bone marrow are engaged in DNA synthesis.

Mortality of industrial workers exposed to acrylonitrile

OBJECTIVES

This study was designed to evaluate the relationship between occupational exposure to acrylonitrile and cancer mortality.

MATERIALS AND METHODS

Workers (18079 white men, 4293 white women, 2191 nonwhite men, and 897 nonwhite women) employed in acrylonitrile production or use in the 1950s through 1983 were followed through 1989 for vital status and cause of death. Exposure-response relationships were evaluated from quantitative estimates of historical exposures. Tobacco use was determined for a sample of workers to assess potential confounding. Mortality rates between the exposed and unexposed workers in the cohort were compared using the Poisson regression.

RESULTS

Analyses by cumulative, average, peak, intensity, duration, and lagged exposure revealed no elevated risk of cancers of the stomach, brain, breast, prostate or lymphatic and hematopoietic systems. Mortality from lung cancer was elevated for the highest quintile of cumulative exposure. When the decile categories were used, the relative risk did not continue to increase at higher levels. Adjustment for cigarette use reduced the risk for lung cancer only slightly. Separate analyses for wage and salaried workers, long-term and short-term workers, fiber and nonfiber plants, and individual plants revealed no clear exposure-response patterns.

CONCLUSIONS

The results indicate that exposure to acrylonitrile at the levels studied is not associated with an increased relative risk for most cancers of a priori interest. The excess of lung cancer in the highest quintile of cumulative exposure may indicate carcinogenic activity at the highest levels of exposure, but analyses of exposure-response do not provide strong or consistent evidence for a causal association.

Exposure assessment for a study of workers exposed to acrylonitrile

Procedures used to develop estimates of exposure to acrylonitrile for a cohort study (>25000 workers in 8 monomer, fiber, and resin companies from 1952 to 1983) are presented. Visits to the companies were made, interviews of workers were conducted, historical records were made, and measurements were taken. On the basis of similar tasks, locations, other exposures, and a similar distribution of exposures to acrylonitrile, 3600 exposure groups were formed. Special procedures were used to reduce the misclassification of workers performing tasks that varied in time but that were inadequately reflected in the job title. A software program organized and retained all exposure information on each exposure group. Quantitative estimates of acrylonitrile exposure were developed using a hierarchical approach in a software program that documented the derivation of each estimate and facilitated data review. Two of the estimation methods were evaluated in a comparison with measurement data.

Agricultural use of DDT and risk of non-Hodgkin's lymphoma: pooled analysis of three case-control studies in the United States

OBJECTIVES

The objective of this pooled analysis was to examine whether exposure to DDT was associated with the risk of non-Hodgkin's lymphoma among male farmers.

METHODS

Data from three case-control studies from four midwestern states in the United States (Nebraska, Iowa, Minnesota, Kansas) were pooled to carry out analyses of 993 cases and 2918 controls. Information on use of agricultural pesticides and other risk factors was based on interviews. Non-farmers (people who had never lived or worked on a farm) were used as a reference category.

RESULTS

There were 161 cases and 340 controls who reported use of DDT on animals or crops, or on both, yielding an odds ratio (OR) of 1.2 (95% confidence intervals (95% CI) 1.0 to 1.6). Farmers who had used DDT for > or = 15 years had an OR of 1.5 (95% CI 1.0 to 2.3). Adjustment for respondent status and use of other pesticides resulted in slightly reduced ORs. Analyses by the number of days of use a year was limited to the Nebraska data. The most notable increase was found among farmers who used DDT for > or = 5 days a year (OR 2.6, 95% CI 1.1 to 5.9); however, additional adjustment for use of organophosphates, phenoxyacetic acids, and the individual pesticides lindane, malathion, and atrazine reduced the ORs to 1.0, 0.9, 1.1, 1.6, and 1.9 respectively.

CONCLUSIONS

No strong consistent evidence was found for an association between exposure to DDT and risk of non-Hodgkin's lymphoma. It seems that the excess risk initially found may be explained by use of other pesticides.

Factors associated with self-reported, pesticide-related visits to health care providers in the agricultural health study

To investigate factors associated with pesticide-related visits to health care providers (i.e., doctor or hospital visits), responses to self-administered questionnaires received from 35,879 licensed restricted-use pesticide applicators participating in the Agricultural Health Study were analyzed. (In Iowa, applicators are actually certified, whereas in North Carolina they are licensed; for ease of reference, the term license will be used for both states in this paper.) The cohort reported a total of more than 10.9 million pesticide-application days. These applications were associated with one or more pesticide-related health care visits by 2,214 applicators (7.0% of the applicator cohort for whom health care visit data were available). The odds of a pesticide-related health care visit were increased for commercial applicators compared to private applicators [odds ratio (OR = 1.77; 95% confidence interval (CI), 1.52-2.06) and for applicators who used insecticides 70 times or more in their lifetime compared to those who used insecticides less frequently (OR = 1.43; CI, 1.26-1.63). After adjusting for the number of applications in a logistic regression model, significantly higher odds of health care visits were observed among North Carolina applicators compared to Iowa applicators (OR = 1.35; CI, 1.17-1.52), among applicators who mixed their own pesticides (OR = 1.65; CI, 1. 22-2.23), and among applicators who personally repaired their pesticide application equipment at least once per year (OR = 1.12; CI, 1.06-1.25). Significantly lower odds were found among female versus male applicators (OR = 0.68; CI, 0.46-0.99) and among applicators who graduated from high school versus those who did not (OR = 0.82; CI, 0.71-0.94 for high school graduates and OR = 0.79; CI, 0.68-0.91 for those with at least some college). Several methods of pesticide application to crops, seed, or stored grain were also associated with significantly elevated odds ratios of health care visits. These observations suggest that several steps can be taken to reduce the number of health care visits resulting from occupational exposure to pesticides. The implications of this pattern of pesticide-related health care visits may have etiologic implications for cancer and other chronic diseases.

The impact of initial job assignment on formaldehyde exposure among African-American and white formaldehyde industry workers

We compared initial job assignments of African-American and white employees at eight worksites that used formaldehyde between 1940 and 1979. Unexposed workers were excluded. Median, ambient air formaldehyde, 8-hour, time-weighted average (TWA8) exposure estimates were determined for each worksite. Job assignments with TWAs above the worksite's median TWA8 were called high formaldehyde exposed (HFE). Job assignments with TWAs less than or equal to the worksite's median TWA8 for the same period were called lower formaldehyde exposed (LFE). Two worksites assigned black workers to HFE jobs in significantly higher proportions than white workers in some decades. One worksite assigned white workers in significantly higher proportions than black workers to HFE jobs in some decades. One worksite assigned racial groups in nearly equal proportions from 1940 to 1969. The remaining sites showed insignificant assignment disproportions (alpha = 0.05; Chi-square < or = 3.841, 1 degree of freedom) for any period. No major trend was apparent across all plants and decades.

Parental occupational exposures and risk of childhood cancer

Occupational exposures of parents might be related to cancer in their offspring. Forty-eight published studies on this topic have reported relative risks for over 1000 specific occupation/cancer combinations. Virtually all of the studies employed the case-control design. Occupations and exposures of fathers were investigated much more frequently than those of the mother. Information about parental occupations was derived through interviews or from birth certificates and other administrative records. Specific exposures were typically estimated by industrial hygienists or were self-reported. The studies have several limitations related to the quality of the exposure assessment, small numbers of exposed cases, multiple comparisons, and possible bias toward the reporting of positive results. Despite these limitations, they provide evidence that certain parental exposures may be harmful to children and deserve further study. The strongest evidence is for childhood leukemia and paternal exposure to solvents, paints, and employment in motor vehicle-related occupations; and childhood nervous system cancers and paternal exposure to paints. To more clearly evaluate the importance of these and other exposures in future investigations, we need improvements in four areas: a) more careful attention must be paid to maternal exposures; b) studies should employ more sophisticated exposure assessment techniques; c) careful attention must be paid to the postulated mechanism, timing, and route of exposure; and d) if postnatal exposures are evaluated, studies should provide evidence that the exposure is actually transferred from the workplace to the child's environment.

Mortality and cancer incidence of aircraft maintenance workers exposed to trichloroethylene and other organic solvents and chemicals: extended follow up

OBJECTIVES

To extend the follow up of a cohort of 14,457 aircraft maintenance workers to the end of 1990 to evaluate cancer risks from potential exposure to trichloroethylene and other chemicals.

METHODS

The cohort comprised civilians employed for at least one year between 1952 and 1956, of whom 5727 had died by 31 December 1990. Analyses compared the mortality of the cohort with the general population of Utah and the mortality and cancer incidence of exposed workers with those unexposed to chemicals, while adjusting for age, sex and calendar time.

RESULTS

In the combined follow up period (1952-90), mortality from all causes and all cancer was close to expected (standardised mortality ratios (SMRs) 97 and 96, respectively). Significant excesses occurred for ischaemic heart disease (SMR 108), asthma (SMR 160), and cancer of the bone (SMR 227), whereas significant deficits occurred for cerebrovascular disease (SMR 88), accidents (SMR 70), and cancer of the central nervous system (SMR 64). Workers exposed to trichloroethylene showed non-significant excesses for non-Hodgkin's lymphoma (relative risk (RR) 2.0), and cancers of the oesophagus (RR 5.6), colon (RR 1.4), primary liver (RR 1.7), breast (RR 1.8), cervix (RR 1.8), kidney (RR 1.6), and bone (RR 2.1). None of these cancers showed an exposure-response gradient and RRs among workers exposed to other chemicals but not trichloroethylene often had RRs as large as workers exposed to trichloroethylene. Workers exposed to solvents other than trichloroethylene had slightly increased mortality from asthma, non-Hodgkin's lymphoma, multiple myeloma, and breast cancer.

CONCLUSION

These findings do not strongly support a causal link with trichloroethylene because the associations were not significant, not clearly dose-related, and inconsistent between men and women. Because findings from experimental investigations and other epidemiological studies on solvents other than trichloroethylene provide some biological plausibility, the suggested links between these chemicals and non-Hodgkin's lymphoma, multiple myeloma, and breast cancer found here deserve further attention. Although this extended follow up cannot rule out a connection between exposures to solvents and some diseases, it seems clear that these workers have not experienced a major increase in cancer mortality or cancer incidence.

Non-hodgkin's lymphoma and agricultural use of the insecticide lindane

Data from population-based case-control studies of non-Hodgkin's lymphoma among white men from Kansas, Nebraska, Iowa, and Minnesota were pooled to evaluate potential risks from environmental exposures in more detail, while controlling for potential confounding factors. These data provided the opportunity to evaluate the risk of non-Hodgkin's lymphoma from potential exposures to lindane, a pesticide that causes cancer in laboratory animals and has been associated with human cancer in a few epidemiologic investigations. This pooled data set includes 987 individuals with non-Hodgkin's lymphoma and 2,895 population-based controls. Information was obtained by telephone or in person interviews, which included detailed questions on farm practices and agricultural use of chemicals. Logistic regression was used to calculate odds ratios (ORs) adjusted for age, state of residence, and subject or proxy interviews. Reported use of lindane significantly increased the risk of non-Hodgkin's's lymphoma by 50%. Some use characteristics were suggestive of an association. ORs were greater among persons who first used the pesticide 20 years before diagnosis (OR = 1.7) than more recently (OR = 1.3), among those who reported more frequent use (OR = 2.0 for use 5 or more days per year versus 1.6 for fewer than five days per year), and from use on crops (OR = 1.9), rather than from use on animals (OR = 1.3), although these differences were not statistically significant. On the other hand, ORs were lower when based on direct interviews (OR = 1.3) than on data from proxy respondents (OR = 2.1) and adjustment for potential confounding by use of 2,4-D and diazinon reduced the ORs associated with lindane use from 1.5 to 1.2 and 1.3, respectively. Lindane does not appear to be a major etiologic factor in the development of non-Hodgkin's's lymphoma, although a small role cannot be ruled out.

Long-term health effects of the occupational exposure to DDT. A preliminary report

We conducted a proportional mortality study of 1043 deaths among men who took part in an antimalarial campaign in Sardinia, Italy from 1946 to 1950. DDT comprised 94% of the insecticide used during the campaign, and was sprayed over the soil of the entire region at an average concentration of 10 mg/m2, as well as in all dwellings and animal shelters. Expected deaths were derived from the proportional mortality rates of the general Italian male population, specific by cause, 5-year age groups, and 5-year calendar periods in the period from 1956 to 1992. The proportional mortality ratio (PMR) for cardiovascular diseases was significantly decreased, while nonmalignant respiratory diseases showed a 22% increase in risk of borderline statistical significance. Significant increases in risk among workers exposed to DDT in application or inspection jobs were observed for liver and biliary tract cancer (PMR = 228; 95% C.I. = 143-345) and multiple myeloma (PMR = 341; 95% C.I. = 110-795). The PMR for myeloid leukemia was also increased (PMR = 189; 95% C.I. = 38-552), although it was not statistically significant. PMRs for liver and biliary tract cancer and myeloid leukemia were also elevated among workers who did not have direct occupational contact with DDT (liver and biliary cancer: PMR = 210; 95% C.I. = 117-346; myeloid leukemia: PMR = 170; 95% C.I. = 19-614). No trends occurred according to length of employment in exposed jobs. These preliminary results are somewhat in agreement with experimental studies in rodents and previous epidemiologic findings. Expansion of the cohort to include all applications, and collection of information to improve exposure assessment is needed to clarify these findings.

Preferential adhesion of fetal liver derived primitive haemopoietic progenitor cells to bone marrow stroma

The orderly transfer of haemopoiesis from the fetal liver to the medullary cavities during the ontogeny may result from a decrease in the capacity of the fetal liver to support haemopoiesis. Alternatively it could be facilitated by the preferential migration of primitive haemopoietic cells to the marrow. In this study we have compared the ability of high proliferative potential colony forming cells (HPP-CFC) derived from murine fetal liver (FL) on the 15th day of gestation and from murine adult bone marrow (BM) to adhere to either FL or BM derived stromal layers. Adhesion of FL HPP-CFC to bone marrow stromal layers was significantly greater than all other combinations tested. The remarkable affinity of HPP-CFC derived from FL for BM stromal layers is consistent with the preferential migration of haemopoietic cells from the fetal liver to the medullary cavities.

Tobacco, alcohol use, and risks of laryngeal and lung cancer by subsite and histologic type in Turkey

Effects of tobacco smoking and alcohol use on risks of cancers of the larynx and lung have been evaluated extensively in industrialized countries. Few studies on the effect of these risk factors have been reported from developing countries. We conducted a case-control study to evaluate risks of laryngeal and lung cancers in men by subsite and cell type in relation to smoking and alcohol drinking in Turkey, a country where smoking and alcohol consumption patterns are different from those in industrialized countries. We identified 832 laryngeal and 1,210 lung cancer cases and 829 controls with information on smoking and alcohol use (amount and duration) and histologic cell type from an oncology treatment center of a Social Security Agency hospital in Istanbul, Turkey, admitted between 1979 and 1984. Both laryngeal and lung cancer showed significant associations with smoking and alcohol drinking, but no monotonic dose-response was obtained for alcohol drinking. Among smokers, the highest risks were observed in the supraglottis region of the larynx (odds ratio [OR] = 4.1) after adjustment for age and alcohol use. Among alcohol drinkers, the highest risks were observed in the glottis region of the larynx (OR = 1.7) after adjustment for age and smoking. In the analysis by the cell type of lung cancer among ever-smokers, small cell type showed the highest risk (OR = 5.4), while it showed no association with alcohol drinking. Cumulative cigarette use (pack-years) and number of cigarettes per day showed stronger associations than years smoked for both cancer sites. The relative risks of joint exposure to smoking and alcohol were 12.2 for laryngeal cancer and 14.1 for lung cancer among heavy smokers and heavy alcohol drinkers. This study provides epidemiologic evidence from Turkey that smoking and alcohol use are associated with risks of cancers of the larynx and lung.

Dichlorodiphenyltrichloroethane serum levels and breast cancer risk: a case-control study from Mexico

Some, but not all, epidemiological studies have suggested that dichlorodiphenyltrichloroethane (DDT) may play a role in the development of breast cancer. These investigations have been conducted in countries where this substance has been banned for at least 20 years. We conducted a study in Mexico, a country in which DDT is still being used to control malaria. In a hospital-based case-control study, we compared 141 histologically confirmed cases of breast cancer with 141 age-matched controls (+/-3 years). All subjects were identified at three referral hospitals of Mexico City between March 1994 and April 1996. Reproductive histories and other variables were obtained by structured interviews, DDT/DDE levels were determined in serum by gas-liquid chromatography. The arithmetic mean of serum DDE in lipid basis was 562.48 +/- 676.18 ppb (range, 10.24-4661.44) for the cases and 505.46 +/- 567.22 ppb (range, 0.004 to 4361.75) for the controls, but this difference was not statistically significant. The age-adjusted odds ratios for breast cancer regarding the serum level of DDE were 0.69 (95% confidence interval, 0.38-1.24) and 0.97 (confidence interval, 0.55-1.70) for the contrasts between tertile 1 (lowest level) and tertiles 2 and 3, respectively. These estimates were unaffected by adjustment for body mass, accumulated time of breast-feeding and menopause, and other breast cancer risk factors. These results do not lend support to the hypothesis that DDT is causally related to breast cancer at the body-burden levels found in our study population but do not exclude the possibility that higher levels of exposure could still play a role in the etiology of this tumor.

A nested case-control study of non-Hodgkin lymphoma and serum organochlorine residues

BACKGROUND

The steady worldwide increase in the incidence of non-Hodgkin lymphoma during the past few decades remains mostly unexplained. Several studies suggest that there may be an association between the agricultural use of the organochlorine 1,1,1-trichloro-2,2'bis(p-chlorophenyl)ethane (DDT) and increased risk of non-Hodgkin lymphoma. We have investigated the association between risk of non-Hodgkin lymphoma and body burden of selected organochlorines in the general population in a nested case-control study.

METHODS

We measured prediagnostic serum concentrations of DDT, its metabolites, and other organochlorines, including polychlorinated biphenyls (PCBs), in 74 cases of non-Hodgkin lymphoma and 147 matched controls identified from a prospective cohort of 25,802 adults, established in 1974 in Washington County, Maryland, USA. We report results for total lipid-corrected serum concentrations of DDT and total PCBs.

FINDINGS

There was a strong dose-response relation between quartiles of total lipid-corrected serum PCB concentrations and risk of non-Hodgkin lymphoma overall (odds ratios by quartile: 1.0; 1.3 [95% CI 0.5-3.3]; 2.8 [1.1-7.6]); and 4.5 [1.7-12.0]; p for trend = 0.0008) and separately in men and in women. There was also evidence suggesting that seropositivity for the Epstein-Barr virus early antigen potentiated the effects of serum PCBs. By contrast, total lipid-corrected serum concentrations of DDT were not associated with risk of non-Hodgkin lymphoma.

INTERPRETATION

These results should be regarded as hypothesis-generating. Before causal inferences can be made about exposure to PCBs and increased risk of non-Hodgkin lymphoma, our findings require replication and the biological plausibility of the association needs further investigation.

Proportional mortality of dichloro-diphenyl-trichloroethane (DDT) workers: a preliminary report

The authors conducted a proportional mortality study of 1,043 deaths that occurred between 1956 and 1992 among men who used mainly dichloro-diphenyl-trichloroethane (DDT) in an anti-malarial campaign in Sardinia, Italy, during the late 1940s. For each cause of interest, investigators compared observed deaths with expected deaths. The estimated DDT exposure ranged from 170 to 600 mg/m3 in indoor operations and from 24 to 86 mg/m3 in outdoor operations. Workers directly exposed to DDT had a significant increase in risk for liver and biliary tract cancers (PMR = 228; 95% confidence interval = 143, 345) and multiple myeloma (PMR = 341; 95% confidence interval = 110, 795). However, the PMR for liver and biliary tract cancers was also elevated among workers who did not have direct occupational contact with DDT, and the authors observed no increase in either PMR, by number of days in exposed jobs. Perhaps DDT did not increase the risk or perhaps occupational exposure, although quite high, did not further increase the risk, compared with the heavy baseline exposure of the entire Sardinian population, (i.e., mainly through diet and drinking water). Expansion of the cohort to include all exposed workers, and collection of information to improve exposure assessment are needed to clarify these findings.

Why immunise. Care giver understanding of childhood immunisation

Currently in Australia, both the National Health and Medical Research Council (NHMRC) and the Public Health Association have stated that our immunisation uptake levels are not of a high enough percentage within the population to prevent outbreaks of childhood vaccine preventable diseases (1996). While the literature discusses factors that are believed to influence care givers' decisions to vaccinate their children, few Australian studies focus on care giver understanding of childhood diseases and vaccination. The purpose of this descriptive study was to profile care givers who presented their children for vaccination at public health clinics regarding their level of understanding of childhood vaccine preventable diseases. Two hundred and forty eight care givers attending one of six public clinics were asked to respond verbally to a researcher administered questionnaire. Demographic information as well as information related specifically to immunisation was collected from each participant. The major findings of this preliminary study indicate a very low level of knowledge among careers presenting their child for vaccination at the public health clinic. Twenty-three percent of carers had no knowledge regarding the vaccinations that their child was receiving and the disease for which the vaccination was administered. In fact, 18 percent of care givers were unsure of the relationship between vaccination and the likelihood of their child contracting an infectious disease. The personal health record was not found to be useful as an educational resource. Although 99 percent of care givers had the booklet in their possession only 8 percent had referred to it as a source of information. The major sources of information were identified as child health nurses (44%) and hospital midwives (34%). The results of this study highlight the disparity in knowledge levels among care givers with regards to vaccination and the diseases they prevent and the important role of the midwife and child health nurse in disseminating information relating to immunisation.

Informational needs of women with a recent diagnosis of breast cancer: development and initial testing of a tool

This study developed and tested the Toronto Informational Needs Questionnaire-Breast Cancer (TINQ-BC), a questionnaire designed to identify the information which women with a recent diagnosis of breast cancer need to deal with their illness. The 73-item questionnaire had content validity based on findings in the literature and opinions of expert oncology nurses. It was administered to 114 women with a recent diagnosis of breast cancer during chemotherapy (n = 39), radiation therapy (n = 40) or surgery (n = 35). Item analysis determined that 51 items in five subscales should be retained in the questionnaire. The subscales, labelled Disease, Investigative Tests, Treatments, Physical, and Psychosocial had good internal consistency reliabilities with Cronbach's alphas of 0.81 to 0.93. Informational needs of women were high with mean scores over 200 in a possible range of 51-255. Informational needs were greatest in either the Disease or Treatments subscales. Marital status, level of education, and level of income were not related to level of informational need. Younger women had a greater need for information than older women (r = -0.35, P = 0.003). The results suggest that information is important to help women with breast cancer manage their illness. Nurses should give women an opportunity to ask questions and be prepared to give accurate information.

Reactive chemicals and cancer

Epidemiologic evidence on the relation between reactive chemicals and cancer is reviewed. These highly reactive chemicals (acrylonitrile; bis[chloromethyl]ether and chloromethyl methyl ether; 1,3-butadiene, ethylene oxide; formaldehyde; mustard gas; sulfuric acid; and vinyl chloride) vary in use and exposure. All are animal carcinogens that also have received considerable epidemiologic attention. Acrylonitrile is a chemical of current economic importance. The epidemiologic evidence is quite weak, but the available studies were very small. Epidemiologic studies clearly demonstrate that bis (chloromethyl) ether and chloromethyl methyl ether cause lung cancer. Continued follow-up of exposed workers is encouraged to provide information on risks for other cancers. Results from epidemiologic studies of butadiene-exposed workers are somewhat inconsistent, but the largest study with the best exposure assessment found the largest relative risk for leukemia. The failure of several larger studies to replicate the early Swedish findings of a very strong association between leukemia and ethylene oxide has not been adequately explained. Epidemiologic studies of formaldehyde provide limited evidence for an association with cancer of the nasopharynx and possibly with nasal cancer. These very rare tumors, however, are difficult to study epidemiologically. Mustard gas is a well-established lung carcinogen, but a recent follow-up of the English cohort suggests that other sites also may be affected. Sulfuric acid appears to cause laryngeal cancer. A suggested relationship with lung cancer in a few studies is of concern because of the widespread opportunity for exposure from ambient air pollution. Vinyl chloride causes angiosarcoma of the liver, but a large, multi-country study provided no clear evidence that other sites are affected.

Lack of expression of Thy-1 (CD90) on acute myeloid leukemia cells with long-term proliferative ability in vitro and in vivo

Acute myeloid leukaemia (AML) is thought to be maintained by a small population of leukemic progenitor cells. To define the phenotype of such cells with long-term proliferative capacity in vitro and in vivo, we have used the production of leukemic clonogenic cells (CFU) after 2 to 8 weeks in suspension culture as a measure of these cells in vitro and compared their phenotype with that of cells capable of engrafting nonobese diabetic severe combined immune deficient (NOD/SCID) mice. Leukemic blast peripheral blood cells were evaluated for expression of CD34 and Thy-1 (CD90) antigens. The majority of AML blast cells at diagnosis lacked expression of Thy-1. Most primary CFU-blast and the CFU detected at up to 8 weeks from suspension cultures were CD34+/Thy-1-. AML cells that were capable of engrafting NOD/SCID mice were also found to have the CD34+/Thy-1- phenotype. However, significant engraftment was achieved using both CD34+/Thy-1- and CD34- subfractions from one AML M5 patient. These results suggest that while heterogeneity exists between individual patients, the leukemic progenitor cells that are capable of maintaining the disease in vitro and in vivo differ from normal hematopoietic progenitor cells in their lack of expression of Thy-1.

Pesticides and cancer

The authors discuss pesticide exposure in both agricultural and nonagricultural occupations, referring to a variety of studies on the cancer risks of specific pesticides. Adult and childhood cancer are addressed, and direction for future research efforts is offered.

Tobacco and non-Hodgkin's lymphoma: combined analysis of three case-control studies (United States)

The role of tobacco in the etiology of non-Hodgkin's lymphoma (NHL) was evaluated in a combined analysis of data from three population-based case-control studies conducted in four midwestern states of the United States: Nebraska, Iowa, Minnesota, and Kansas. Interviews were obtained from 1,177 cases (993 men, 184 women) and 3,625 controls (2,918 men, 707 women) or, if deceased, from their next-of-kin. Overall, there was no association between NHL and tobacco use (odds ratio [OR] = 1.0, 95 percent confidence interval [CI] = 0.8-1.1) or cigarette smoking (OR = 1.0, CI = 0.8-1.1). A slight negative association evident in analyses by intensity and duration of smoking was not present when interviews from proxy respondents were eliminated. There was a suggestion of a positive association between smoking and NHL among women (OR = 1.3, CI = 0.9-1.9), although there was no clear exposure-response relationship. This large case-control analysis provides no evidence that smoking is linked to the development of NHL among men. The possible role of smoking in the etiology of NHL among women needs further evaluation.