Cancer mortality among chemical workers in an Italian plant

Malignant Mesothelioma in Rome and Latium Region, 1993-2001

Aims and background

Epidemiological studies on malignant mesothelioma have provided evidence on the etiologic role of occupational asbestos exposure and, to some extent, domestic and residential exposures. Less attention has been given to the occurrence of mesothelioma in urban areas where large quantities of asbestos have been employed in the past. The purpose of the study was to investigate the occurrence of mesothelioma in patients living in the urban area of Rome and in other parts of the Latium Region and the patterns of asbestos exposure.

Methods and study design

A pathology-based, malignant mesothelioma archive operating in Rome, Italy, was the source of cases. Included in the survey were cases resident in Latium and diagnosed in the period January 1, 1993, through December 31, 2001. Information on asbestos exposure was derived from interviews to the patient or his/her next of kin and from available medical records.

Results

The case series included: 114 males and 53 females; total, 167. Information on asbestos exposure was available for 138 cases (83%). Occupational exposure was ascertained or suspected for 33% of cases resident in Rome and 63% of those resident in other municipalities of Latium. Sex ratio was 1.6 in Rome and 3.3 in Latium.

Conclusions

The high prevalence of women among mesothelioma cases and lower proportion of occupational exposure in Rome versus the other municipalities of Latium suggest a possible role of environmental asbestos exposure in the urban area.

Theoretical study on the reaction mechanism of chlordimeform with OH radicals

A theoretical investigation on the multiple-channel degradation mechanism of chlordimeform with OH radicals in the atmosphere was completed using a dual-level direct dynamics method. The equilibrium geometries and the corresponding harmonic vibrational frequencies of the stationary points were obtained at the M06-2X/6-311++G(d,p) level. The minimum energy paths (MEP) were calculated at the same level, and energetic information was further refined at M06-2X/6-311++G(3df,2p) level. The rate constants for the 15 reaction channels were calculated by improved canonical variational transition state theory with small-curvature tunneling correction over the temperature range 200-1,000 K. The total rate constants are in good agreement with the available experimental data and the three-parameter expression k(T) =2.62 × 10(-18)  T (2.71) exp (899.61/T) cm(3)molecule(-1) s(-1) was given. The calculated results indicate that the addition reaction of the carbon-nitrogen double bond is the major channel, while the abstraction reaction from the benzene ring of chlordimeform is the least competitive channel.

Critical review and synthesis of the epidemiologic evidence on formaldehyde exposure and risk of leukemia and other lymphohematopoietic malignancies

Purpose

Recent epidemiologic studies indicate elevated risks for some lymphohematopoietic malignancies (LHM) related to formaldehyde exposure. We performed a systematic review of literature to assess the strength and consistency of associations.

Methods

We summarized published literature in the PubMed database of the National Library of Medicine during 1966–2012. Literature was categorized according to study design and population: industrial cohort studies, professional cohort studies, and population-based case–control studies.

Results

Findings from occupational cohort and population-based case–control studies were very inconsistent for LHM, including myeloid leukemia. Apart from some isolated exceptions, relative risks were close to the null, and there was little evidence for dose–response relations for any of the LHM.

Conclusions

At present, there is no consistent or strong epidemiologic evidence that formaldehyde is causally related to any of the LHM. The absence of established toxicological mechanisms further weakens any arguments for causation. To be informative, future epidemiologic research should improve on formaldehyde exposure assessment and apply modern diagnostic schemes for specific LHM.

A review and meta-analysis of formaldehyde exposure and leukemia

Most reviews on the carcinogenicity of formaldehyde have focused on cancers of the respiratory tract because these cancer sites were thought to be most biologically plausible. However, two recent updated large industrial studies have found positive associations between some measures of formaldehyde exposure and increased leukemia, although another recent update of a large study did not find any association. We examine 18 epidemiology studies of workers exposed to formaldehyde where leukemia rates were reported. We summarize the findings across studies by using meta-analytic techniques to calculate the meta-relative risk values (mRR), confidence intervals, and heterogeneity of the risk estimates for several study characteristics. We also determine if publication or reporting biases may be affecting the estimates. We found a small increase in rate of leukemia overall among embalmers (mRR = 1.6, 95%CI 1.2-6.0), and pathologists/anatomists (mRR = 1.4, 95%CI 1.0-1.9). Industrial workers, who have been reported to have the highest formaldehyde exposures, had a mRR of 0.9 (95%CI 0.8-1.0). There was increased risk with increasing exposure in two large industrial studies, although the increased risk is one of these studies was not seen when an external comparison group is used. Also, another large industrial study with more highly exposure workers found decreased risk of leukemia among the highest exposed group. The long latency for leukemia deaths observed in the two industrial studies that reported increased risk was not consistent with a chemical carcinogen such as benzene. We found limited evidence of publication or reporting bias. On balance, these data do not provide consistent support for a relationship between formaldehyde exposure and leukemia risk.

A meta-analysis of cohort studies describing mortality and cancer incidence among chemical workers in the United States and western Europe

We evaluated the mortality and cancer experience of employees of the chemical industry in the United States and western Europe, as reported in the peer-reviewed literature between 1966 and 1997 (>1 million workers and >15 million person-years). Cohort studies (N = 461) were grouped (N = 181) so that specific populations could be traced from the earliest to the most recently published report, and we extracted observed and expected numbers of cases for each of 35 mortality and 23 cancer incidence endpoints. We then generated standardized mortality ratios or standardized incidence ratios and 95% confidence intervals, and undertook meta-analyses of subcohorts (for example, gender, latency, or duration of employment), as well as the entire cohort. With few exceptions, the observed cause-specific mortality and site-specific cancer incidences were reassuring: overall, 10% fewer deaths were observed than expected. Fewer than expected deaths from all causes, cardiovascular disease, noncancer respiratory disease, cirrhosis of the liver, and external causes were observed, some or all of which may be attributed to a "healthy worker effect." Meta-analyses revealed weak to moderate excesses of lung and bladder cancers likely caused by occupational exposure to known human carcinogens. We also observed a 10-15% increase in lymphatic and hematopoietic cancers. Additional research is required to gain a more complete understanding of the potential role that methodology and environmental or occupational influences may play in these associations.

A review and meta-analysis of formaldehyde exposure and pancreatic cancer

BACKGROUND

Most reviews on the carcinogenicity of formaldehyde have focused on cancers of the respiratory tract. Two recent studies have suggested that exposure to formaldehyde may increase the risk for pancreatic cancer.

METHODS

We examine 14 epidemiology studies of workers exposed to formaldehyde where pancreatic cancer rates were reported and use meta-analytic techniques to summarize the findings. We also rank formaldehyde exposures for the industries in these studies.

RESULTS

We found a small increase of pancreatic cancer risk in the studies overall (meta Relative Risk [mRR] 1.1, 95%CI 1.0-1.3); however, this increased risk was limited to embalmers (mRR 1.3, 95%CI 1.0-1.6) and pathologists and anatomists (mRR 1.3, 95%CI 1.0-1.7). There was no increased risk among industrial workers (mRR 0.9, 95%CI 0.8-1.1) who on average had the highest formaldehyde exposures.

CONCLUSIONS

A small increased risk of pancreatic cancer from formaldehyde exposure cannot be ruled out from the studies examined. However, the null findings among industrial workers and the lack of biological plausibility would argue against formaldehyde as a cause. The increased risk of pancreatic cancer among embalmers, pathologists, and anatomists may be due to a diagnostic bias or to occupational exposures other than formaldehyde in these professions.