Risk assessment of the occupational contact with ammonium

The aim of the cohort retrospective study was to analyze and evaluate the influence of certain factors (age, profession, smoking) on the characteristics and the incidence rate of the upper respiratory tract diseases (URTDs) in the occupational contact with ammonium. Subjects were 180 men, divided into 3 professional groups. The average shift concentrations of ammonium were measured in the permanent work places and individually by personal passive dosemeters. The URTDs were classified into 15 groups according to localization and the stage of the inflammatory process. The relationships "time-response" and "dose (concentration)-response" were determined. The factor "cumulative exposure" was used in order to evaluate the actual noxious effect of NH3 on the mucose of the upper respiratory tract (URT). There was a statistically reliable difference found in the incidence rate of atrophic rhinitis, hypertrophic pharyngitis and laryngitis, and neoplasms of the URT in the workers with the highest cumulative exposure. For this group relative risk was 4.00, 2.22, 3.20 and 4.00, respectively, with 95% Cl. The "cumulative exposure" factor gives the best proofs for the toxic effect of ammonium and a possibility for assessment of the relative risk.

Environmental exposure to tremolite and respiratory cancer in New Caledonia: a case-control study

A case-control study on respiratory cancers was conducted in New Caledonia (South Pacific), where a high incidence of malignant pleural mesothelioma had been observed. The disease pattern suggested an environmental exposure to asbestos. The first results showed that, in some areas, tremolite asbestos derived from local outcroppings was used as whitewash (locally named "pö"). All cases diagnosed between 1993 and 1995 (including 15 pleural mesotheliomas, 228 lung cancers, and 23 laryngeal cancers) and 305 controls were included in the study. Detailed information on past or present use of the whitewash, residential history, smoking, diet, and occupation was collected. The risk of mesothelioma was strongly associated with the use of the whitewash (odds ratio (OR) = 40.9; 95% confidence interval (CI): 5.15, 325). All Melanesian cases had been exposed. Among Melanesian women, exposure to the whitewash was associated with an increased risk of lung cancer (OR = 4.89; 95% CI: 1.13, 21.2), and smokers exposed to po had an approximately ninefold risk (OR = 9.26; 95% CI: 1.72, 49.7) compared with women who never smoked and had never used the whitewash. In contrast, no association was noted between exposure to pö and lung cancer risk among Melanesian men, probably because of lower exposure levels. Among non-Melanesians, the numbers of exposed subjects were too small to assess the effect of exposure to po. There was no indication of elevated risks for the other cancer sites.

Socioeconomic status, social mobility and cancer occurrence during working life: a case-control study among French electricity and gas workers

OBJECTIVES

A case-control study within a cohort of the workers employed by Electricité de France and Gaz de France between 1988 and 1992 was carried out to investigate relationships between cancers and socioeconomic status, including the effects of social mobility, by studying three professional career points.

METHODS

All the incident cases of breast cancer in women and all the incident cases of upper respiratory and digestive tract cancer (comprising cancers of the larynx, pharynx, buccal cavity and esophagus), lung cancer, hematopoietic system cancers and colon cancer in men were extracted from the Cancer Register of the Social Security Department. The controls were matched for age (men) and for age and length of employment in the company (women). Socioeconomic status was measured at three professional career points (beginning, midpoint (about 35), and time of diagnosis (about 48)) by two types of socio-professional variables: employee category (low, medium, high) and a variable based on the French socioeconomic status classification system. An estimation of social mobility was done between career beginning and midpoint. Cases and controls were compared for socioeconomic status at the three career points. They were also compared for social mobility.

RESULTS

The differences between the social categories were larger at the start than later in the career for breast cancer in women. The category of operations staff was used as a reference, and this analysis shows a difference between the risks associated with supervisors (OR = 2.0) and managers and specialist professions (OR = 1.5). There were large differences according to the type of cancer in men. A socioeconomic gradient in the incidence of cancers of the upper respiratory and digestive tract was observed at every career stage. The gradient was largest at the moment of diagnosis. The odds ratio was 3.4 for supervisors, 7.8 for operations staff and 14.8 for production staff. There was a socioeconomic gradient in lung cancer at all points in the career and in the incidence of the hematopoietic system cancers at mid-career and at diagnosis. No association between socioeconomic status and colon cancer was found. Social mobility accentuated all these results.

CONCLUSION

Socioeconomic status is involved in the development of cancers. Our study suggests that the transition from social to biological processes could act via specific lifestyle and/or work-related risk factors. When there is a social gradient in the incidence of a cancer, an individual's social change is at least as important as his/her original social status in the relationship between cancer and social class.

Proliferative lesions in swimbladder of Japanese medaka Oryzias latipes and guppy Poecilia reticulata

Thirteen cases of proliferative lesions of the swimbladder were encountered in Japanese medaka Oryzias latipes and guppy Poecilia reticulata from about 10,000 medaka and 5000 guppies used in carcinogenicity tests and histologically examined. Two of the 4 cases from medaka and 8 of the 9 from guppies occurred in untreated control specimens. The lesions affected the gas gland epithelium and included hyperplasia, adenoma, and adenocarcinoma. One medaka had hyperplasia of the gas gland epithelium and in 1 guppy the gland was enlarged with an increase in the number of epithelial layers. Gas gland adenomas, 3 cases in medaka and 1 in the guppy, were typically larger than the hyperplastic lesions, formed expansive masses up to 1 mm in greatest dimension, and exhibited a solid or glandular growth pattern and mild cellular pleomorphism. Adenocarcinoma was the most advanced lesion and all 7 cases occurred in guppies. Adenocarcinomas sometimes filled the entire swimbladder and measured up to 2.5 mm in diameter. Cells of adenocarcinomas were highly pleomorphic, with atypical nuclei, and an elevated mitotic activity. Because most of these tumors occurred in fish from control groups or in tests with noncarcinogenic compounds, the lesions observed here are probably spontaneous rather than chemically induced. Their rare occurrence, however, makes swimbladder proliferative lesions in small-fish carcinogenesis models sensitive indicators of compounds that might target cells of the gas gland.

Cancer in California school employees, 1988-1992

BACKGROUND

Periodic concerns about excesses of cancer among teachers in California schools prompted our examination of cancer incidence in California school employees.

METHODS

Records of school employees between 1987-1992 were linked to the California Cancer Registry of incident cases diagnosed 1988-1992. Sex-, race-, and age-adjusted standardized incidence ratios were calculated for specific cancer sites. Analyses stratified by sex, race/ethnicity, and job assignment were also performed.

RESULTS

Melanoma of the skin, thyroid cancer, prostate cancer, and female cancers of the breast, uterus, and ovary all occurred more frequently than expected in these school employees. In contrast, cancers of the respiratory system, oral cavity, digestive system, urinary system, and uterine cervix occurred less frequently.

CONCLUSIONS

The incidence of cancers thought to be related to hormones and/or higher socioeconomic status appeared elevated while cancers often linked to smoking and/or alcohol intake occurred less frequently in this large cohort of professional school employees.

Initial results from the national registry for juvenile-onset recurrent respiratory papillomatosis. RRP Task Force

OBJECTIVE

To characterize the spectrum of juvenile-onset recurrent respiratory papillomatosis (RRP) in the United States and to obtain data about the natural course of the disease and its response to treatment.

SETTING

Twenty tertiary-care pediatric otolaryngology centers throughout the United States.

PATIENTS

All patients with active RRP aged less than 18 years at the participating sites.

MAIN OUTCOME MEASURES

Number of surgical procedures performed per year, progression of papillomas to previously nondiseased anatomical sites, drug interventions and other adjuvant therapy, and need for tracheostomy.

RESULTS

Data were collected from 399 children enrolled from January, 1, 1997, through December 31, 1998. There were 51.9% male; 62.7% white, 28.3% black, 9.0% other or unknown racial group; 10.8% Hispanic ethnicity. Mean age at diagnosis was 3.8 years (range, 0.1-16.3 years) and mean duration of disease was 4.4 years (range, 0.03-18.9 years). The mean number of surgical procedures per child was 4.4 per year (range, 0.2-19.3 per year). Children whose RRP was diagnosed at younger ages (<3.0 years) were 3.6 times more likely to have more than 4 surgical procedures per year (P=.001) and almost 2 times more likely to have 2 or more anatomical sites affected (P=.008) than were children whose RRP was diagnosed at later ages (> or =3.0 years), after adjusting for sex, race, and years of treatment.

CONCLUSIONS

Children whose disease was diagnosed before age 3 years were more likely than children aged 3 years or older to have more severe disease as measured by the mean number of surgical procedures performed and by the number of anatomical sites affected. The registry will form the basis for future analysis on the outcome of disease, natural course of RRP under management strategies, prevention strategies, and public health importance.

Effect of cigar smoking on the risk of cardiovascular disease, chronic obstructive pulmonary disease, and cancer in men

BACKGROUND

The sale of cigars in the United States has been increasing for the past six years. Cigar smoking is a known risk factor for certain cancers and for chronic obstructive pulmonary disease (COPD). However, unlike the relation between cigarette smoking and cardiovascular disease, the association between cigar smoking and cardiovascular disease has not been clearly established.

METHODS

We performed a cohort study among 17,774 men 30 to 85 years of age at base line (from 1964 through 1973) who were enrolled in the Kaiser Permanente health plan and who reported that they had never smoked cigarettes and did not currently smoke a pipe. Those who smoked cigars (1546 men) and those who did not (16,228) were followed from 1971 through the end of 1995 for a first hospitalization for or death from a major cardiovascular disease or COPD, and through the end of 1996 for a diagnosis of cancer.

RESULTS

In multivariate analysis, cigar smokers, as compared with nonsmokers, were at higher risk for coronary heart disease (relative risk, 1.27; 95 percent confidence interval, 1.12 to 1.45), COPD (relative risk, 1.45; 95 percent confidence interval, 1.10 to 1.91), and cancers of the upper aerodigestive tract (relative risk, 2.02; 95 percent confidence interval, 1.01 to 4.06) and lung (relative risk, 2.14; 95 percent confidence interval, 1.12 to 4.11), with evidence of dose-response effects. There appeared to be a synergistic relation between cigar smoking and alcohol consumption with respect to the risk of oropharyngeal cancers and cancers of the upper aerodigestive tract.

CONCLUSIONS

Independently of other risk factors, regular cigar smoking can increase the risk of coronary heart disease, COPD, and cancers of the upper aerodigestive tract and lung.

Lymphoma at uncommon sites

Lymphoma can often present in unusual situations. This article provides a comprehensive review of the literature in which both non-Hodgkin's lymphoma and Hodgkin's disease are discussed.

Carcinoid syndrome: a statistical evaluation of 748 reported cases

No statistical evaluation of patients with carcinoid syndrome in a reliable number of cases has been available in the past 35 years. To update our knowledge about the syndrome, we have evaluated from various clinicopathologic viewpoints a large series of patients with the syndrome reported up to date. The data of 748 patients with the syndrome were collected from 8876 carcinoid patients reported in the literature and analyzed by the Gut-Pancreatic Endocrinoma Analyzing System (the Niigata Registry). The results are summarized as follows. 1) The patients with the syndrome had a tendency to be older than those without it. 2) The incidence of the syndrome was 8.4% of 8876 carcinoid patients. 3) Serotonin activities were extremely high in patients with the syndrome as compared to those without it (91.7% versus 26.6%). 4) The rate of metastases was higher in patients with the syndrome than in those without it (84.8% versus 29.2%), and higher in the liver than in lymph nodes among patients with the syndrome (73.4% versus 37.4%). 5) Flushing and carcinoid heart as most specific clinical manifestations of the syndrome were recorded at 78.3% and 17.4%, respectively. 6) The 5-year survival rate after resection of primary lesions was 76.0% of 304 patients with the syndrome, lower in patients with digestive carcinoids than in those with extradigestive lesions (67.2% versus 88.7%). It is expected that the results obtained in the present evaluation on patients with carcinoid syndrome will provide investigators active in this specialized field with useful and extensive information for their future activities.

Second primary cancers in patients with squamous cell carcinoma of the skin: a population-based study in Sweden

We studied second primary cancer among 25,947 patients diagnosed with squamous cell carcinoma of the skin (SCC) in Sweden between 1958 and 1992. In total, 5,706 patients developed a second primary cancer at any site, compared with an expected number of 2,651 [standardized incidence ratio (SIR) = 2.15; 95% confidence interval (CI) = 2.10-2.21]. Men below 60 years of age at diagnosis of SCC had higher SIR (2.5; CI = 2.2-2.8) with the highest risk during the first year of follow-up (SIR = 9.2; CI = 6.9-12.2). If second primary SCC was excluded, the SIR was reduced to 1.30 (CI = 1.25-1.34); the relationships by sex, age and time since diagnosis remained similar. For skin cancer, the SIR for second SCC was markedly elevated (SIR = 15.6) and the risk of malignant melanoma was elevated 3-fold. Significantly increased risks were found for most second cancers in squamous cell epithelium: lip (SIR = 5.2), respiratory organs (SIR = 1.7), esophagus (SIR = 1.5), cervix uteri (SIR = 2.2), and vulva including vagina (SIR = 2.3). There was a generally increased risk of almost 2-fold for second cancer in hematopoietic or lymphoproliferative tissues. Slightly increased rates (SIR = 1.0-1.5) were seen for second tumors in digestive tissues. Finally, a high SIR (SIR = 5.5) was observed for second primary cancer in salivary glands. In conclusion, patients with SCC are at increased risk to develop new primary cancer, especially in skin, squamous cell epithelial and tobacco-related tissues. Common risk factors among the tumor types might explain our findings, however, an intrinsic susceptibility among SCC patients to develop cancer is also possible.

Comparative incidence of de novo nonlymphoid malignancies after liver transplantation under tacrolimus using surveillance epidemiologic end result data

BACKGROUND

An increased incidence of de novo nonlymphoid malignancies has been shown in immunocompromised patients. However, the true risk over time compared to the general population has not been determined.

METHODS

One thousand consecutive patients were carefully followed for an average of 77.8+/-11.1 (range, 56.3-96.3) months after primary liver transplantation at a single center. All de novo nonlymphoid malignancies were recorded. Each malignancy was compared with a standard Occupational Cohort Mortality Analysis Program population matched for age, sex, and length of follow-up using modified life table technique and surveillance epidemiology end result (SEER) data.

RESULTS

Fifty-seven patients accounted for de novo malignancies and contributed 4795.3 total person years, a mean+/-SD of 36+/-21 (median, 36; range, 6-74) months after liver transplantation. Twenty-two of these malignancies were skin malignancies including two melanomas. Oropharyngeal cancers (n=7) were found to be 7.6 times higher (P<0.05) and respiratory malignancies (n=8) were 1.7 times higher (P>0.05) compared to the SEER incidence rate. Female reproductive system malignancies including breast cancer (n=3) were 1.9 times lower (P>0.05) and genitourinary malignancies were (n=5) 1.5 times lower (P>0.05) than their matched cohorts. No differences was observed in gastrointestinal malignancies (n=5). There was a significant difference in survival of the patients after diagnosis of malignancy depending on the type of cancer. There were two Kaposi's sarcomas, two metastatic unknown primaries, one thyroid, one brain, and one ophthalmic malignancies in the series. Mortality for Kaposi's and metastatic disease of unknown primary was 100% within 5 months, while the 1-year mortality for oropharyngeal cancer was 57.1% and that for lung cancers was 62.5%. Long-term survival for skin cancer was highest: 86.4% at 3 years (P=0.015 by log-rank test).

CONCLUSION

An increased incidence of de novo cancers in the chronically immunocompromised patient demands careful long-term screening protocols which will help to facilitate the diagnosis at an early stage of the disease. This is particularly true for oropharyngeal cancers where the risk is more than 7 times higher compared to SEER incidence data matched for age, sex, and length of follow-up.

Recurrent respiratory papillomatosis

Recurrent respiratory papillomatosis is a disease characterized by the growth of wart-like neoplasms anywhere along the aerodigestive tract. The etiologic agent is the human papillomavirus, of which 90 subtypes have been described. The age distribution of those affected appears to be a bimodal curve, with the first peak around 5 years of age and the second occurring in adults in the third decade of life. The mainstay of treatment is surgical resection to maintain an adequate airway; patients often require multiple surgeries. The epidemiology, pathogenesis, clinical features, and treatment options are discussed. Current evidence regarding prognosis and the multifactorial nature of pathogenesis are also reviewed.

Risk factors for juvenile onset recurrent respiratory papillomatosis

BACKGROUND

Children born to condylomatous mothers are at risk for developing juvenile onset recurrent respiratory papillomatosis (JORRP). We inquired whether the triad of vaginal delivery, being firstborn and maternal age of <20 years are also risk factors for JORRP.

METHODS

Data for JORRP and adult onset recurrent respiratory papillomatosis cases were obtained from questionnaires answered by patients or their parents for the Recurrent Respiratory Papillomatosis Foundation. The observed numbers of cesarean births, first order births and births to mothers <20 years old were compared with expected numbers for the same variables, which were computed by distributing the cases by year of birth and then applying to them national annual statistics for the year of birth. In addition observed and expected numbers of first order births to mothers <20 years old were compared with corresponding numbers in mothers 20 years old or older.

RESULTS

In JORRP cases the relationships be tween observed and expected numbers of cases were as follows: cesarean births, 4.6-fold less; first order births, 1.6-fold greater; maternal age <20 years old, 2.6-fold greater. All these differences were statistically highly significant. The observed parity effect was mediated to a large extent by maternal age. In contrast there were no significant differences between observed and expected numbers of adult onset recurrent respiratory papillomatosis cases with respect to any of the above variables.

CONCLUSIONS

Young primiparous mothers with condylomas are at a high risk for transmission of JORRP to their infants. The option of cesarean delivery should be discussed with a mother who has condyloma at the time of delivery.

Spontaneous tumours in tree shrews (Tupaia belangeri): population studies

In a necropsy series at the German Primate Centre, 63 of 1132 tree shrews were found to have tumours. The youngest affected animal was < 6 months old, but the incidence of tumours increased strikingly beyond 2 years of age; of 17 animals aged > 8 years, no less than 14 (82.4%) were affected. The sites of neoplasia were the genital system (22 cases), haematopoietic system (18 cases of malignant lymphoma, many involving the digestive tract), lungs (14 cases), integument (five cases), digestive tract (three cases other than those with malignant lymphoma) and urinary bladder (one case).

[Second primary malignant neoplasms in patients treated in the Otolaryngology Clinic AM of Lodz in the years 1981-1989]

The incidence of multiple primary malignant tumours in 913 patients treated during 9 years for malignant neoplasms was investigated. In 24 (2.63%) cases second primary malignant neoplasm was diagnosed, mostly (in 19 cases-2.1%) it was correlated to cancer of larynx. In 18 cases (75% of all multiple tumours) neoplasms were metachronous, in 5-synchronous, and in one case--it was multifocal neoplasm (in both tonsils). In 3 patients three separate primary neoplasms were observed.

[Epidemiology of malignant neoplasms of the upper respiratory tract and oral cavity in the Bydgoszcz region]

The authors performed epidemiological analysis of malignant neoplasms of the nose, paranasal sinuses, throat, tongue, larynx and salivary glands in Bydgoszcz area. All the patients were treated in the Otolaryngological Clinic of Medical Academy in Bydgoszcz. Patient's sex, age, profession, living and environmental conditions as well as histopathological diagnosis were taken into analysis. The data were referred to various regions of Bydgoszcz province, which were elucidated on the basis of microclimate conditions, industry, soil conditions, density of the forest area, and cultivated agriculture plants. Correlations between occurrence of oral cavity and the upper respiratory tract malignant neoplasms and living conditions as well as kind of profession in different parts of Bydgoszcz province were estimated.

Cancer incidence, morbidity and geothermal air pollution in Rotorua, New Zealand

BACKGROUND

The New Zealand city of Rotorua sits on a geothermal field. However, little is known about the possible health impacts of the geothermal emissions. This was an ecological study that examined cancer incidence and morbidity data for Rotorua.

METHODS

Cancer registry and hospital discharge (morbidity) data were obtained for the decade 1981-1990. Standardized incidence ratios (SIR) were calculated comparing Rotorua residents with those living in the rest of New Zealand. Diagnostic categories examined were based on known target organ systems of hydrogen sulphide toxicity.

RESULTS

Of the cancer sites, there was an elevated rate for nasal cancers. However, this was based on only four cases. The SIR for cancers of the trachea, bronchus and lung in Maori women was 1.48 (95% CI: 1.03-2.06). This was not explained by higher smoking rates. In the hospital discharge data, a number of diseases showed elevated SIR, notably diseases of the nervous system and the eye. To some extent, these effects were characteristic of effects induced by hydrogen sulphide and also mercury compounds. However, there were few data with which to assess whether significant mercury exposures had occurred, and other explanations were possible.

CONCLUSIONS

There are inadequate exposure data for Rotorua to permit conclusions on likely causal associations. However, some of the elevated disease rates were at least consistent with what one might expect to find if sufficient exposures to hydrogen sulphide and/or mercury were occurring.

Alcohol drinking, social class and cancer

This chapter reviews the data on occurrence of cancers that are potentially caused by alcohol drinking (cancers of the upper gastrointestinal and respiratory tracts, and liver cancer) in relation to social class. In order to assess the role of alcohol drinking in the observed social class gradients of these cancers, we have particularly looked for consistency in the gradients of different alcohol-related cancers, and used lung cancer occurrence to judge the role of tobacco smoking, which is the major other determinant of these diseases. Additional data on levels of alcohol drinking and on the occurrence of other alcohol-related morbidity are brought into the discussion where available. A role of alcohol drinking in the observed negative social class gradients for alcohol-related cancers is very likely in men in France, Italy and New Zealand. Evidence that is less strong, but is suggestive of a role of alcohol drinking, is seen for men in Brazil, Switzerland, the United Kingdom and Denmark. Although a role of alcohol drinking is likely or possible in certain populations, other factors may contribute as well, most notably tobacco smoking and dietary habits. Additional data on the frequency of complications after surgical procedures in alcohol drinkers are reviewed briefly.

Socioeconomic differences in cancer incidence and mortality

This chapter summarizes accumulated data on the presence, magnitude and consistency of socioeconomic differentials in mortality and incidence of all malignant neoplasms and 24 individual types of neoplasms in 37 populations in 21 countries. More or less consistent excess risks in men in lower social strata were observed for all respiratory cancers (nose, larynx and lung) and cancers of the oral cavity and pharynx, oesophagus, stomach, and, with a number of exceptions, liver, as well as for all malignancies taken together. For women, low-class excesses were consistently encountered for cancers of the oesophagus, stomach, cervix uteri and, less consistently, liver. Men in higher social strata displayed excesses of colon and brain cancers and skin melanoma. In the two Latin American populations for which data were available, lung cancer was more frequent in higher social strata. Excesses in high female socioeconomic strata were seen in most populations for cancers of the colon, breast and ovary and for skin melanoma. Longitudinal data from England and Wales suggested widening over time of social class differences in men for all cancers combined and for cancers of the lung, larynx and stomach, and in women for all cancers combined and for cervical cancer.

Cancer risks in the Kaluga oblast of the Russian Federation 10 years after the Chernobyl accident

Cancer morbidity and mortality were studied in areas of the Kaluga oblast contaminated with radionuclides. The main objective of the study was to assess the influence of radiation exposure on existing levels of cancer morbidity and mortality. Time trends and relative population risks were analysed. Based on this analysis, it was concluded that the current levels of morbidity from cancers among the populations residing in the studied areas were primarily a result of a complex of factors which predated the exposure from the Chernobyl accident. However, there seems to be an unfavourable trend concerning malignant neoplasms of the respiratory organs for women residing in the contaminated areas. To date, no statistically significant effect of radiation on cancer morbidity (except for thyroid cancer in women) has been noted. The levels of cancer morbidity and mortality in the contaminated areas generally reflect the changes in cancer incidence in the oblast as a whole. The findings are consistent with international data on latent periods for the induction of radiogenic cancers and the biological effects for similar levels of exposure to populations residing in contaminated territories. Further studies are necessary in order to monitor possible effects that are related to the accident.

An updated meta-analysis of formaldehyde exposure and upper respiratory tract cancers

In this study, we summarize 47 epidemiologic studies related to formaldehyde exposure and use meta-analytic techniques to assess findings for cancers of the lung, nose/nasal sinuses, and nasopharynx. Our analyses indicate that workers with formaldehyde exposure have essentially null findings for lung cancer and a slight deficit of sinonasal cancer. Nasopharyngeal cancer rates were elevated moderately in a minority of studies. Most studies, however, did not find any nasopharyngeal cancers, and many failed to report their findings. After correcting for underreporting, we found a meta relative risk of 1.0 for cohort studies. Case-control studies had a meta relative risk of 1.3. Our review of the exposure literature indicated that the nasopharyngeal cancer case-control studies represented much lower and less certain exposures than the cohort studies. We conclude that the available studies do not support a causal relation between formaldehyde exposure and nasopharyngeal cancer. This conclusion conflicts with conclusions from two previous meta-analyses, primarily because of our consideration of unreported data.

Epidemiologic evidence on the relationship between mists containing sulfuric acid and respiratory tract cancer

This review identified and evaluated 25 epidemiologic studies pertaining to the carcinogenicity of mists containing sulfuric acid (MSA). Few studies were designed with acid mists as the principal exposure under investigation, and in all studies exposure assessment was limited. The results of the follow-up studies from industries with high or moderate exposure potential and the case-control studies indicate, in aggregate, a moderate association between MSA and larynx cancer. The data suggest a dose-response relationship. However, many of the results from individual studies are imprecise, and confounding by smoking, alcohol, and other occupational agents is not adequately adjusted for. The biologic plausibility and the possible carcinogenic mechanism remain uncertain. There is little evidence in support of a causal relationship between exposure to MSA and lung cancer. Information is inadequate for drawing any meaningful inference about the association between exposure to MSA and nasal cancer.

What to do about softwood? A review of respiratory effects and recommendations regarding exposure limits

Wood dust has been classified as a human carcinogen by the International Agency for Research on Cancer with a footnote that the evaluation was based on a marked excess of sino-nasal cancer among workers exposed primarily to hardwood dusts. Because the epidemiologic data on the carcinogenic effects of softwoods are weaker than for hardwoods, standard setting for softwood dust presents a greater dilemma. Unfortunately, the studies of wood dust and cancer do not have the quantitative exposure data necessary for standard setting for either hardwoods or softwoods. Asthma, non-asthmatic airflow obstruction, and both upper and lower respiratory symptoms have been associated with exposure to both 'allergenic' and 'non-allergenic' softwood dusts, and an association with increasing intensity of exposure has been observed in multiple studies. The available evidence seems to indicate that to prevent these nonmalignant effects, the level of exposure to all softwood dust should be at least as low 2 mg/m3. A standard of 1 mg/m3 may be more appropriate to provide a safety margin to protect more sensitive workers. It may be that some of the health effects observed are due to the natural components of wood, such as resin acids or monoterpenes, or to molds.