Lesley Richardson

Listing Occupational Carcinogens

The occupational environment has been a most fruitful one for investigating the etiology of human cancer. Many recognized human carcinogens are occupational carcinogens. There is a large volume of epidemiologic and experimental data concerning cancer risks in different work environments. It is important to synthesize this information for both scientific and public health purposes. Various organizations and individuals have published lists of occupational carcinogens. However, such lists have been limited by unclear criteria for which recognized carcinogens should be considered occupational carcinogens, and by inconsistent and incomplete information on the occupations and industries in which the carcinogenic substances may be found and on their target sites of cancer. Based largely on the evaluations published by the International Agency for Research on Cancer, and augmented with additional information, the present article represents an attempt to summarize, in tabular form, current knowledge on occupational carcinogens, the occupations and industries in which they are found, and their target organs. We have considered 28 agents as definite occupational carcinogens, 27 agents as probable occupational carcinogens, and 113 agents as possible occupational carcinogens. These tables should be useful for regulatory or preventive purposes and for scientific purposes in research priority setting and in understanding carcinogenesis.

A prospective epidemiological study of gastrointestinal health effects due to the consumption of drinking water

The objective of this study was to assess if drinking water meeting currently accepted microbiological standards is the source of gastrointestinal illnesses and to attempt to identify the source(s) of these illnesses. A randomized prospective study was conducted over a period of 16 months (September 1993-December 1994) in a middle class suburban community served by a single water filtration plant. A representative sample of 1400 families were selected and randomly allocated in four groups of 350, to the following regimens: (1) tap water; (2) tap water from a continuously purged tap; (3) bottled plant water; (4) purified bottled water (tap water treated by reverse osmosis or spring water). The water treatment plant produced wather that met or exceeded current North American regulations for drinking water quality. The distribution system was found to be in compliance for both coliforms and chlorine. Using the purified water group as the baseline, the excess of gastrointestinal illness associated with tap wa...

The INTERPHONE study: design, epidemiological methods, and description of the study population

The very rapid worldwide increase in mobile phone use in the last decade has generated considerable interest in the possible health effects of exposure to radio frequency (RF) fields. A multinational case–control study, INTERPHONE, was set-up to investigate whether mobile phone use increases the risk of cancer and, more specifically, whether the RF fields emitted by mobile phones are carcinogenic. The study focused on tumours arising in the tissues most exposed to RF fields from mobile phones: glioma, meningioma, acoustic neurinoma and parotid gland tumours. In addition to a detailed history of mobile phone use, information was collected on a number of known and potential risk factors for these tumours. The study was conducted in 13 countries. Australia, Canada, Denmark, Finland, France, Germany, Israel, Italy, Japan, New Zealand, Norway, Sweden, and the UK using a common core protocol. This paper describes the study design and methods and the main characteristics of the study population. INTERPHONE is the largest case–control study to date investigating risks related to mobile phone use and to other potential risk factors for the tumours of interest and includes 2,765 glioma, 2,425 meningioma, 1,121 acoustic neurinoma, 109 malignant parotid gland tumour cases and 7,658 controls. Particular attention was paid to estimating the amount and direction of potential recall and participation biases and their impact on the study results.

Validation of short term recall of mobile phone use for the Interphone study

Aim: To validate short term recall of mobile phone use within Interphone, an international collaborative case control study of tumours of the brain, acoustic nerve, and salivary glands related to mobile telephone use. Methods: Mobile phone use of 672 volunteers in 11 countries was recorded by operators or through the use of software modified phones, and compared to use recalled six months later using the Interphone study questionnaire. Agreement between recalled and actual phone use was analysed using both categorical and continuous measures of number and duration of phone calls. Results: Correlations between recalled and actual phone use were moderate to high (ranging from 0.5 to 0.8 across countries) and of the same order for number and duration of calls. The kappa statistic demonstrated fair to moderate agreement for both number and duration of calls (weighted kappa ranging from 0.20 to 0.60 across countries). On average, subjects underestimated the number of calls per month (geometric mean ratio of recalled to actual = 0.92, 95% CI 0.85 to 0.99), whereas duration of calls was overestimated (geometric mean ratio = 1.42, 95% CI 1.29 to 1.56). The ratio of recalled to actual use increased with level of use, showing underestimation in light users and overestimation in heavy users. There was substantial heterogeneity in this ratio between countries. Inter-individual variation was also large, and increased with level of use. Conclusions: Volunteer subjects recalled their recent phone use with moderate systematic error and substantial random error. This large random error can be expected to reduce the power of the Interphone study to detect an increase in risk of brain, acoustic nerve, and parotid gland tumours with increasing mobile phone use, if one exists.

Recall bias in the assessment of exposure to mobile phones

Most studies of mobile phone use are case–control studies that rely on participants’ reports of past phone use for their exposure assessment. Differential errors in recalled phone use are a major concern in such studies. INTERPHONE, a multinational case–control study of brain tumour risk and mobile phone use, included validation studies to quantify such errors and evaluate the potential for recall bias. Mobile phone records of 212 cases and 296 controls were collected from network operators in three INTERPHONE countries over an average of 2 years, and compared with mobile phone use reported at interview. The ratio of reported to recorded phone use was analysed as measure of agreement. Mean ratios were virtually the same for cases and controls: both underestimated number of calls by a factor of 0.81 and overestimated call duration by a factor of 1.4. For cases, but not controls, ratios increased with increasing time before the interview; however, these trends were based on few subjects with long-term data. Ratios increased by level of use. Random recall errors were large. In conclusion, there was little evidence for differential recall errors overall or in recent time periods. However, apparent overestimation by cases in more distant time periods could cause positive bias in estimates of disease risk associated with mobile phone use.

Quantifying the Impact of Selection Bias Caused by Nonparticipation in a Case–Control Study of Mobile Phone Use

PURPOSE To quantitatively assess the impact of selection bias caused by nonparticipation in a multinational case-control study of mobile phone use and brain tumor. METHODS Non-response questionnaires (NRQ) were completed by a sub-set of nonparticipants. Selection bias factors were calculated based on the prevalence of mobile phone use reported by nonparticipants with NRQ data, and on scenarios of hypothetical exposure prevalence for other nonparticipants. RESULTS Regular mobile phone use was reported less frequently by controls and cases who completed the NRQ (controls, 56%; cases, 50%) than by those who completed the full interview (controls, 69%; cases, 66%). This relationship was consistent across study centers, sex, and age groups. Lower education and more recent start of mobile phone use were associated with refusal to participate. Bias factors varied between 0.87 and 0.92 in the most plausible scenarios. CONCLUSIONS Refusal to participate in brain tumor case-control studies seems to be related to less prevalent use of mobile phones, and this could result in a downward bias of around 10% in odds ratios for regular mobile phone use. The use of simple selection bias estimation methods in case-control studies can give important insights into the extent of any bias, even when nonparticipant information is incomplete.

Comparison of exposure estimates in the Finnish job-exposure matrix FINJEM with a JEM derived from expert assessments performed in Montreal

Context Retrospective exposure assessment in population-based case–control studies poses a major challenge due to the wide range of occupations and industries involved. The FINJEM is a generic job-exposure matrix (JEM) developed in Finland, which represents a potentially cost-effective exposure assessment tool. While FINJEM has been used in several studies outside Finland, little is known of its applicability in other countries. Methods We compared prevalence and intensity of exposure in FINJEM with a JEM developed from expert assessments of occupational histories obtained in a population-based case–control study in Montreal. Agreement for prevalence of exposure was measured by weighted κ coefficients between prevalence categories. Agreement for exposure intensity was measured by Spearman correlation coefficients between cells with non-null exposure. Results The comparison involved 27 chemicals, the time period 1945–1995 and included 4743 jobs initially assessed by the Montreal experts. 4293 combinations of agent, occupational title and period were available for comparison of prevalence. Agent-specific prevalence was consistently higher in the Montreal JEM (median difference 1.7%). Agent-specific κ values between prevalence categories varied from 0.89 (welding fumes) to 0.07 (flour dust). The comparison of exposure levels involved 14 agents and 198 cells with non-null exposure in both sources. Agent-specific Spearman correlation varied from 0.89 (flour dust) to −0.35 (benzo(a)pyrene). Conclusion Our observations suggest that information concerning several agents (eg, metals, welding fumes) can be successfully transported from Finland to Canada and probably other countries. However, for other agents, there was considerable disagreement, and hence, transportability of FINJEM cannot be assumed by default.

Occupational Exposure to Extremely Low-Frequency Magnetic Fields and Brain Tumor Risks in the INTEROCC Study

Background: Occupational exposure to extremely low-frequency magnetic fields (ELF) is a suspected risk factor for brain tumors, however the literature is inconsistent. Few studies have assessed whether ELF in different time windows of exposure may be associated with specific histologic types of brain tumors. This study examines the association between ELF and brain tumors in the large-scale INTEROCC study. Methods: Cases of adult primary glioma and meningioma were recruited in seven countries (Australia, Canada, France, Germany, Israel, New Zealand, and the United Kingdom) between 2000 and 2004. Estimates of mean workday ELF exposure based on a job exposure matrix were assigned. Estimates of cumulative exposure, average exposure, maximum exposure, and exposure duration were calculated for the lifetime, and 1 to 4, 5 to 9, and 10+ years before the diagnosis/reference date. Results: There were 3,761 included brain tumor cases (1,939 glioma and 1,822 meningioma) and 5,404 population controls. There was no association between lifetime cumulative ELF exposure and glioma or meningioma risk. However, there were positive associations between cumulative ELF 1 to 4 years before the diagnosis/reference date and glioma [odds ratio (OR) ≥ 90th percentile vs. < 25th percentile, 1.67; 95% confidence interval (CI), 1.36–2.07; PLinear trend < 0.0001], and, somewhat weaker associations with meningioma (OR ≥ 90th percentile vs. < 25th percentile, 1.23; 95% CI, 0.97–1.57; PLinear trend = 0.02). Conclusions: Results showed positive associations between ELF in the recent past and glioma. Impact: Occupational ELF exposure may play a role in the later stages (promotion and progression) of brain tumorigenesis. Cancer Epidemiol Biomarkers Prev; 23(9); 1863–72. ©2014 AACR.

Assessing Occupational Exposure to Chemicals in an International Epidemiological Study of Brain Tumours

The INTEROCC project is a multi-centre case-control study investigating the risk of developing brain cancer due to occupational chemical and electromagnetic field exposures. To estimate chemical exposures, the Finnish Job Exposure Matrix (FINJEM) was modified to improve its performance in the INTEROCC study and to address some of its limitations, resulting in the development of the INTEROCC JEM. An international team of occupational hygienists developed a crosswalk between the Finnish occupational codes used in FINJEM and the International Standard Classification of Occupations 1968 (ISCO68). For ISCO68 codes linked to multiple Finnish codes, weighted means of the exposure estimates were calculated. Similarly, multiple ISCO68 codes linked to a single Finnish code with evidence of heterogeneous exposure were refined. One of the key time periods in FINJEM (1960-1984) was split into two periods (1960-1974 and 1975-1984). Benzene exposure estimates in early periods were modified upwards. The internal consistency of hydrocarbon exposures and exposures to engine exhaust fumes was improved. Finally, exposure to polycyclic aromatic hydrocarbon and benzo(a)pyrene was modified to include the contribution from second-hand smoke. The crosswalk ensured that the FINJEM exposure estimates could be applied to the INTEROCC study subjects. The modifications generally resulted in an increased prevalence of exposure to chemical agents. This increased prevalence of exposure was not restricted to the lowest categories of cumulative exposure, but was seen across all levels for some agents. Although this work has produced a JEM with important improvements compared to FINJEM, further improvements are possible with the expansion of agents and additional external data.

Can loud noise cause acoustic neuroma? Analysis of the INTERPHONE study in France

Objectives: To investigate possible associations between risk of acoustic neuroma and exposure to loud noise in leisure and occupational settings. Methods: A case-control study was conducted in France within the international INTERPHONE study. The cases were the 108 subjects diagnosed with acoustic neuroma between 1 June 2000 and 31 August 2003. Two controls per case were selected from the electoral rolls and individually matched for gender, age (5 years) and area (local authority district) of residence at the time of the case diagnosis. Multivariate analyses were conducted using conditional logistic regression. Adjustment was made for socioeconomic status. Results: Acoustic neuroma was found to be associated with loud noise exposure (odds ratio (OR) = 2.55; 95% CI 1.35 to 4.82), both in leisure settings, particularly when listening to loud music (OR = 3.88; 95% CI 1.48 to 10.17) and at work (OR = 2.26; 95% CI 1.08 to 4.72). This risk increased with exposure duration (>6 years’ leisure exposure: OR = 3.15; 95% CI 1.07 to 9.24). Risk varied according to the type of noise (continuous or explosive vs intermittent). Conclusion: The present results agree with other recent reports implicating loud noise in the risk of acoustic neuroma.