Childhood cancer: overview of incidence trends and environmental carcinogens

An estimated 8000 children 0 to 14 years of age are diagnosed annually with cancer in the United States. Leukemia and brain tumors are the most common childhood malignancies, accounting for 30 and 20% of newly diagnosed cases, respectively. From 1975 to 1978 to 1987 to 1990, cancer among white children increased slightly from 12.8 to 14.1/100,000. Increases are suggested for leukemia, gliomas, and, to a much lesser extent, Wilms' tumor. There are a few well-established environmental causes of childhood cancer such as radiation, chemotherapeutic agents, and diethylstilbestrol. Many other agents such as electromagnetic fields, pesticides, and some parental occupational exposures are suspected of playing roles, but the evidence is not conclusive at this time. Some childhood exposures such as secondhand cigarette smoke may contribute to cancers that develop many years after childhood. For some exposures such as radiation and pesticides data suggest that children may be more susceptible to the carcinogenic effects than similarly exposed adults.

High bladder cancer mortality in rural New England (United States): an etiologic study

An interview study of next-of-kin of 325 persons who died of bladder cancer and 673 individuals who died of other causes in Vermont and New Hampshire (United States) was conducted to assess reasons for the persistent pattern of elevated bladder cancer mortality for both genders in rural New England. There are some evidence of elevated risks for both leather and textile workers that rose to over twofold for workers who also lived near these industries and for persons with French-Canadian ancestry. Occupational exposures in the textile and leather industry may explain at least a portion of the excess bladder cancer risk in rural New England.

Cancer incidence and mortality among beta-naphthylamine and benzidine dye workers in Moscow

BACKGROUND

Cancer incidence and mortality were evaluated among 4581 aniline dye production workers in Moscow.

METHODS

A historical cohort was assembled and followed-up from 1 January 1975 to 31 December 1989. Moscow district oncologic dispensary registries furnished case ascertainment and employer records provided job exposure data. Expected cancers and deaths were calculated based on gender-, age-, and calendar time-specific incidence and mortality rates for the Moscow general population applied to the cohort's person-years of follow-up. Disease-specific standardized mortality and incidence values were derived from ratios of observed to expected cancers.

RESULTS

Men experienced elevated total cancer mortality (standardized mortality ratio [SMR] = 125; 95% CI: 110-142) and urinary bladder cancer mortality (SMR = 279; 95% CI: 192-391), and increased all malignancy (standardized incidence ratio [SIR] = 142; 95% CI: 125-160), oesophageal (SIR = 203; 95% CI: 108-347), respiratory tract (SIR = 154; 95% CI: 120-194) and bladder (SIR = 394; 95% CI: 268-559) cancer incidence. Women had elevated oesophageal (SMR = 313; 95% CI: 124-664) and bladder (SMR = 311; 95% CI: 149-571) cancer mortality and elevated all malignancy (SIR = 124; 95% CI: 106-144), oesophageal (SIR = 348; 95% CI: 140-719), and bladder (SIR = 861; 95% CI: 458-8002) cancer incidence. Bladder cancer rate increased with employment duration and younger age first hired. Rate estimates were highest among beta-naphthylamine exposed workers but was also increased among workers with other chemical exposures. A cancer prevention and control effort that limited benzidine exposure to < or = 3 years was apparently unsuccessful as indicated by a significant excess of bladder cancer (SIR = 1773; 95% CI: 356-5180) among these workers.

CONCLUSION

Relative rates of oesophageal, lung, and stomach cancer were also elevated among all workers, but did not increase with total years worked, age first hired, or year first hired, suggesting a non-occupational aetiology.

Increased risk of colorectal cancer among smokers: results of a 26-year follow-up of US veterans and a review

To clarify the relationship between tobacco use and risk of colorectal cancer, we evaluated a cohort of 248,046 American veterans followed prospectively for 26 years. In comparison with veterans who had never used tobacco, the risk of death was significantly increased for colon cancer and rectal cancer among current and former cigarette smokers and among pipe or cigar smokers, controlling for social class and occupational physical activity. Rectal-cancer risk was also significantly elevated among users of chewing tobacco or snuff. For both sites, risk increased significantly with pack-years, earlier age at first use, and number of cigarettes. These results reinforce 2 recent reports of the association of cigarette smoking and colorectal cancer in men and women. Inconsistencies in the findings of earlier epidemiologic studies appear to be due in large part to differences in length of follow-up or in choice of controls. Studies with at least 20 years of follow-up or population-based controls have tended to find elevated risk with tobacco smoking, while those with shorter follow-up or hospital controls have not. This, plus the strength and consistency of the association of smoking and colon polyps, suggest that smoking may primarily affect an early stage in the development of colon cancer. If this association is causal, tobacco use may be responsible for 16% of colon-cancer and 22% of rectal-cancer deaths among these veterans.

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

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

Cancer mortality patterns among female and male workers employed in a cable manufacturing plant during World War II

A cohort mortality study was conducted among 9028 (3042 women, 5986 men) workers potentially exposed to chlorinated naphthalenes (chloracnegens structurally similar to dioxins) and asbestos in the manufacture of Navy cable during World War II. Based on mortality through December 31, 1985, standardized mortality ratios (SMRs) for all cancers was 1.03 in women (95% confidence interval [CI] = 0.9 to 1.17) and 1.18 in men (95% CI = 1.10 to 1.26). There were no significant elevations in causes of death hypothesized a prior to be associated with chlorinated naphthalene exposure (malignant neoplasms [MN] of connective tissue, liver, and lymphatic and hematopoietic organs). An excess of MN of the connective tissue was suggested for workers with over 1 year of exposure and 25 years of latency (SMR = 3.54; 95% CI = 0.97 to 9.07). Among cancer sites not hypothesized to be related a priori, three showed concordant excesses among both genders (MN of stomach; rectum; and trachea, bronchus, and lung). No significant elevations occurred in hormonally related cancers among women. Cancer mortality among 460 individuals with chloracne (431 men, 29 women) was similar to that of the entire cohort, although the chloracne subcohort showed significant excesses in two rare causes of death (MN of esophagus, SMR = 3.26; "benign and unspecified neoplasms," SMR = 4.93). Use of county referent rates decreased SMRs for stomach, rectal, and buccal cavity cancer, suggesting a role for nonoccupational risk factors. It is difficult to draw conclusions about carcinogenicity of chlorinated naphthalenes because of study limitations, most importantly, concomitant asbestos exposure and the relatively short duration of exposure to chlorinated naphthalenes among most of the cohort.

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

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

Inclusion of women and minorities in occupational cancer epidemiologic research

A survey of published epidemiologic studies from eight journals during 1971 to 1990 was conducted to assess the proportion and characteristics of occupational cancer studies that have included women and minorities. A total of 1233 reports included 562 (46%) with subjects limited to white men. The remaining 671 (54%) had subjects from other race-gender groups. Thirty-five percent included white women, but only 14% presented any analyses of white women specifically and only 7% presented more than five risk estimates. The proportions with analyses of nonwhite women (any = 2%; detailed = 1%) or men (any = 7%; detailed = 3%) were also small. Studies with detailed analyses of women and minorities tended to use weaker methodologies (ie, proportionate mortality or cross-sectional design) than the studies of white men and were less able to provide convincing data on the occupational cancer risks of women and minorities.

Cancer among migrant and seasonal farmworkers: an epidemiologic review and research agenda

There are an estimated three million hired migrant and seasonal farmworkers in the United States. Adults and children may be exposed to mutagenic and potentially carcinogenic pesticides during planting, weeding, thinning, and harvesting crops. Field conditions that provide little opportunity to wash skin or clothing to minimize pesticide absorption may intensify exposure. Little is known, however, about the occurrence of cancer in migrant or seasonal farmworkers. Most cancer epidemiologic research on agricultural populations has focussed on farm owner/operators. The few studies that have evaluated cancer in farmworkers suggest that, like farm owner/operators, they may be experiencing excesses of multiple myeloma and cancers of the stomach, prostate, and testis. A few studies suggest that the farmworkers may differ from farmers by experiencing excesses of cancers of the buccal cavity and pharynx, lung, and liver. Cervical cancer was elevated in female farmworkers in one study. Descriptive data and etiologic research on cancer among farmworkers and family members are urgently needed. Feasibility evaluations, however, should precede etiologic investigations because of possible difficulties in studying this population of workers. Issues that need to be evaluated include assessing where and when farmworkers and family members are diagnosed and/or treated for malignancies, the ability of farmworkers to provide histories of crops, locations, and years worked and living conditions, the ability of agricultural experts to determine likely pesticide exposures based on such farmworkers' histories, the ability to obtain information on potential confounding factors, the ability to recontact or determine vital status of specific farmworkers over time, the suitability of conducting studies in home-base vs. upstream counties, and the ability to study agriculturally related malignancies in persons who have left farm work before the disease occurs.

The role of agricultural pesticide use in the development of non-Hodgkin's lymphoma in women

Non-Hodgkin's lymphoma has been found to be associated with agricultural pesticide use in men, but little is known about the risk in women. In a recent population-based, case-control study conducted in eastern Nebraska, no increased risk of non-Hodgkin's lymphoma was found in women who had ever lived or worked on a farm (odds ratio [OR] = 1.0). Neither the use of insecticides (OR = 0.8) nor herbicides (OR = 0.7) on the farm was associated with non-Hodgkin's lymphoma; however, the number of women who mixed or applied pesticides was small, particularly in comparison to men on farms. Small nonsignificant associations were observed among the women who personally handled insecticides (OR = 1.3) or herbicides (OR = 1.2). Women who personally handled organophosphate insecticides had a significant 4.5-fold increased risk of non-Hodgkin's lymphoma. Use of chlorinated hydrocarbon insecticides was associated with an OR of 1.6; however, the use on dairy cattle was associated with a 3-fold increased risk. Pesticide-related risks were greater among women with a family history of cancer, particularly a history of lymphatic or hematopoietic cancer among first-degree relatives.

Are the known bladder cancer risk-factors associated with more advanced bladder cancer?

Risk factors for superficial and invasive bladder cancer were examined in a case-control study of 470 cases identified in 1967-68 in the Brockton and Boston Standard Metropolitan Areas (MA, United States) and of 500 population-based controls. Histologic specimens were reviewed and classified as superficial or invasive, following a standardized protocol. The tobacco-associated risk for superficial bladder cancer was odds ratio (OR) = 2.6 (95 percent confidence interval [CI] = 1.7-4.1) and the risk for invasive bladder cancer was OR = 1.7 (CI = 1.1-2.5). For subjects less than 60 years of age, the risks were greater for invasive tumors (OR = 4.3, CI = 1.2-15) than for superficial tumors (OR = 2.0, CI = 0.9-4.2), but this pattern for tobacco use was not found in older subjects. A strong trend of increased risk with increased amount of cigarettes smoked was shown only for invasive bladder tumors. No clear pattern of excess risk for invasive bladder tumors was seen for age at first use and years since last use of tobacco. The risk associated with occupational exposure to aromatic amine bladder carcinogens was OR = 1.7 (CI = 0.8-3.3) for superficial and OR = 1.5 (CI = 0.8-3.0) for invasive bladder cancer. For subjects less than 60 years of age, the risks were greater for invasive (OR = 12.0, CI = 2.1-65) than for superficial tumors (OR = 4.3, CI = 0.8-24), but this pattern for occupational exposure was not found in older subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Patterns of pesticide use among farmers: implications for epidemiologic research

Epidemiologic studies of farmers have linked pesticides with certain cancers. Information on exposures from many of these studies was obtained by interview of farmers or their next-of-kin. The reliability and validity of data on pesticide use obtained by recall, often years after the event, have been questioned. Pesticide use, however, is an integral component in most agricultural operations, and the farmers' knowledge and recall of chemicals used may be better than for many other occupations. Contrary to general belief, many farmers typically use only a few pesticides during their lifetimes and make only a few applications per year. Data from U.S. Department of Agriculture surveys indicate that herbicides are applied to wheat, corn, soybeans, and cotton and that application of insecticides to corn averages two or fewer times per year. In epidemiologic studies at the National Cancer Institute, the proportion of farmers ever reporting lifetime use of five or more different chemicals was 7% for insecticides and 20% for herbicides. Surrogate respondents have often been used in epidemiologic studies of cancer; they are able to recall pesticide use with less detail than the farmers themselves. The pesticides reported by surrogates were the same as reported by subjects themselves, but with less frequency. Comparison of reporting by cases and controls provided no evidence of case-response (differential) bias; thus, inaccurate recall of pesticide use by subjects or surrogates would tend to diminish risk estimates and dilute exposure-response gradients.

Pesticides and non-Hodgkin's lymphoma

The incidence of non-Hodgkin's lymphoma (NHL) has increased over 50% in the last 15 years. This paper reviews the possible role of pesticides in this increase. While small increases in risk of NHL among farmers have been observed in general occupational surveys, recent studies focusing on specific pesticides have observed much larger risks. Frequent use of phenoxyacetic acid herbicides, in particular, 2,4-dichlorophenoxyacetic acid, has been associated with 2- to 8-fold increases of NHL in studies conducted in Sweden, Kansas, Nebraska, Canada, and elsewhere. Canine malignant lymphoma has also been associated with dog owner use of 2,4-dichlorophenoxyacetic acid and commercial lawn pesticide treatments. There are much fewer data linking NHL to other types of pesticides, but triazine herbicides, organophosphate insecticides, fungicides, and fumigants have also been associated with increased risk of NHL. Pesticide exposures are not limited to agricultural populations but are widespread in the general population through use on lawns, golf courses, rights-of-way, and elsewhere. Since the use of pesticides, particularly phenoxy herbicides, has increased dramatically preceding and during the time period in which the incidence of NHL has increased, they could have contributed to the rising incidence of NHL.

Clues to cancer etiology from studies of farmers

This article summarizes cancer risks among farmers to clarify the magnitude of the problem and to suggest directions for future research. Significant excesses occurred for Hodgkin's disease, multiple myeloma, leukemia, skin melanomas, and cancers of the lip, stomach, and prostate. Nonsignificant increases in risk were also noted for non-Hodgkin's lymphoma and cancers of connective tissue and brain. These excesses occurred against a background of substantial deficits among farmers for total mortality and mortality from many specific diseases. The tumors vary in frequency, histology, and prognosis and do not fall into any obvious grouping. Two commonalities may be important. Several of the tumors excessive among farmers appear to be rising in the general population and are excessive among patients with naturally occurring or medically induced immunodeficiencies. Therefore epidemiologic studies on specific exposures among farmers may help explain the rising trend of certain cancers in developed countries and provide clues to mechanisms of action for environmental carcinogens.

Soft tissue sarcoma and tobacco use: data from a prospective cohort study of United States veterans

A report of an increased risk of soft tissue sarcoma (STS) among users of smokeless tobacco led us to evaluate this association and the role of other types of tobacco in a prospective cohort mortality-study of United States veterans. A total of 248,046 veterans provided tobacco-use histories on a mail questionnaire in 1954 or 1957. Data on subsequent tobacco use were not collected. By 1980, 119 deaths from STS had occurred among the cohort members. Veterans who had ever chewed tobacco or used snuff had a nonsignificant 40 percent excess of STS (95 percent confidence interval [CI] = 0.8-2.6; 21 deaths) in comparison with veterans who had never used any tobacco products. Risk was limited to former users (relative risk [RR] = 1.5) with no excess seen among current users (RR = 0.9). Frequent former users had higher risk (RR = 1.9) than infrequent users (RR = 1.3). Risk was slightly higher in persons who started using smokeless tobacco at younger ages, but did not increase with duration of use or with late age at cessation of use. Most veterans who used chewing tobacco or snuff also used some other form of tobacco. No STS deaths occurred among the 2,308 veterans who used smokeless tobacco only. An unexpected finding of the study was the significant excess of STS deaths among cigarette smokers (RR = 1.8, CI = 1.1-2.9). Risk was higher among ex-smokers (RR = 2.2) than among current smokers (RR = 1.5) and was not related to number of cigarettes per day, age started smoking, duration, or pack-years.(ABSTRACT TRUNCATED AT 250 WORDS)

Occupational cancer mortality among urban women in the former USSR

Occupational cancer mortality was evaluated among approximately three million female pensioners from urban areas of the former USSR. In 1970, these women experienced 14,918 cancer deaths. Occupational data were obtained from death certificates and the 1970 USSR National Population Census. Thirty-five occupational groups, including nine predominantly professional or office-work groups and 26 groups involving physical labor, were evaluated. The expected mortality rates were based on the urban female population of the USSR in 1970. Data for all cancer sites combined, and cancers of the esophagus, stomach, colon, rectum, lung, breast, cervix, and hematopoietic system are presented. Among all female pensioners, there were significant increases of all cancers combined (rate ratio [RR] = 1.05), and cancers of the breast (RR = 1.3), cervix (RR = 1.3), and the hematopoietic system (RR = 1.2), and a significant deficit of cancer of the esophagus (RR = 0.8). Many well-established associations between cancer and occupation among men were observed among the study group of female pensioners, such as stomach and lung cancer among miners, and hematopoietic malignancies among scientists and physicians. Other associations, to be investigated further, also were observed, such as excess lung cancer among waitresses. The peak employment period for this cohort of women was during World War II and the postwar period, when Soviet women outnumbered men almost two-to-one. Consequently, many of the women held jobs that are typically held by men. Thus, this study provides valuable information on occupational risks to women that may be relevant in other countries where women increasingly are being employed in jobs traditionally held by men.

Use of hair coloring products and the risk of lymphoma, multiple myeloma, and chronic lymphocytic leukemia

OBJECTIVES

Hair coloring products are widely used and contain components that are mutagenic and carcinogenic. An association between occupational exposure to hair coloring products and hematopoietic cancers has been reported, but the risk for these cancers among users has not been carefully evaluated.

METHODS

We conducted a population-based, case-control study with telephone interviews from 385 with telephone interviews from 385 non-Hodgkin's lymphoma cases, 70 Hodgkin's disease cases, 72 multiple myeloma cases, 56 chronic lymphocytic leukemia cases, and 1432 controls.

RESULTS

Among women, use was associated with odds ratios of 1.5 for non-Hodgkin's lymphoma, 1.7 for Hodgkin's disease, 1.8 for multiple myeloma, and 1.0 for chronic lymphocytic leukemia. Risk was higher for permanent hair coloring products than for semi- or nonpermanent products, particularly for dark colors. Long duration and early age of first use tended to increase risk, but the patterns were inconsistent. Use was much less common in men and did not significantly increase risk.

CONCLUSIONS

The use of hair coloring products appears to increase the risk of non-Hodgkin's lymphoma. Multiple myeloma and Hodgkin's disease were also associated, although based on far fewer subjects. If these results represent a causal association, use of hair coloring products would account for 35% of non-Hodgkin's lymphoma cases in exposed women and 20% in all women.

A prospective study of tobacco use and multiple myeloma: evidence against an association

The relationship between the use of cigarettes and other tobacco products and the risk of multiple myeloma was examined in a cohort of nearly 250,000 American veterans followed prospectively for 26 years. Compared with men who had never tobacco, the risk of death from myeloma was not increased among current (relative risk [RR] = 0.9, 95 percent confidence interval [CI] = 0.8-1.2) or former (RR = 1.0, CI = 0.8-1.3) cigarette smokers, nor among users of chewing tobacco or snuff (RR = 1.0, CI = 0.4-2.3). Risk was only slightly and nonsignificantly increased among pipe or cigar smokers (RR = 1.2, CI = 0.9-1.5). There was no indication of increasing risk with amount of tobacco used or earlier age at first use. With over 90 percent power to detect a 30 percent increased risk of this tumor occurring among current cigarette smokers, this study provides the strongest evidence to date against an association of cigarette smoking with multiple myeloma.