Environmental and Occupational Risk Factors for Amyotrophic Lateral Sclerosis: A Case-Control Study

Abstract

Background/Aims: Environmental and occupational exposures are implicated as risk factors for amyotrophic lateral sclerosis (ALS), the etiology of which is largely unknown, although no causal relationships have been established. Objective: The aim of the study was to evaluate the associations of personal risk factors and self-reported environmental and occupational exposures with risk of ALS. Methods: The cases involved ALS patients (n = 66) identified from major neurological centers in Pittsburgh and Philadelphia, Pa., USA, from 2008 to 2010. The age-, race- and sex-matched controls included outpatient hospital and population-based controls (n = 66). A detailed questionnaire obtaining data on occupation, vocational and avocational exposure as well as personal lifestyle factors was administered. Results: Occupational exposure to metals (odds ratio, OR = 3.65; 95% CI: 1.15, 11.60) and pesticides (OR = 6.50; 95% CI: 1.78, 23.77) was related to increased risk of ALS after controlling for smoking and education. No associations were found for occupational exposure to organic or aromatic solvents. Conclusion: Workers exposed to metals and pesticides may be at greater risk of ALS. Future research should involve more accurate exposure assessment through the use of job exposure matrices, confirmation of occupation and biomarkers.

Exposure to hazardous air pollutants and the risk of amyotrophic lateral sclerosis

“…Here we report an association with aromatic solvents that was not observed in our prior investigation of environmental and occupational exposures. Associations between occupational exposure to metals and pesticides and an increased risk of ALS, after adjustment for smoking, education, and other exposure groups were reported by our previous study (Malek et al, 2014). Possible mechanisms for the observed association between ambient air concentrations of aromatic solvents and the risk of ALS include peripheral neuropathy (Gobba et al, 1995) or autonomic nervous system activity dysfunction (Murata et al, 1991;Beck et al, 2005).…”

“…One study also included a panel of industrial hygienists (McGuire et al, 1997). Some studies have reported a significant association between exposure to solvents or occupations involving solvent exposure and ALS or MND (Morahan and Pamphlett, 2006;Chio et al, 1991;Chancellor et al, 1993;Graham et al, 1997;Park et al, 2005;Pamphlett, 2012), while others have not (Malek et al, 2014;McGuire et al, 1997;Fang et al, 2009;Gunnarsson et al, 1992;Hawkes and Fox, 1981;Gait et al, 2003;Strickland et al, 1996;Savettieri et al, 1991;Granieri et al, 1988;Welp et al, 1996;Gunnarsson et al, 1991). Two studies reported increased mortality from MND among leather workers (Hawkes and Fox, 1981;Buckley et al, 1983), but another did not find this association (Gunnarsson and Lindberg, 1989;Martyn, 1989).…”

“…Cases were diagnosed with ALS from November 1998eMarch 2010, with the majority (63.6%) of diagnoses occurring between January 2008 and March 2010. Details of the study methods have been previously reported (Malek et al, 2014). Of the 106 eligible cases, 78 participated in the overall study (73.6% response rate) and 66 cases (57 from W. Pa and 9 from Philadelphia) were included in the analysis as controls were not identified for twelve cases.…”

Occupational exposure and amyotrophic lateral sclerosis in a prospective cohort

“…A subsequent study, conducted after the meta-analyses, showed no elevated risk of ALS mortality and exposure to pesticides but did show increased risks for several specific pesticides, including exposure to aldrin and dieldrin 14. Malek et al 36 and Yu et al 43 also showed an association between occupational exposure to pesticides and ALS incidence. We found a non-significant, negative association between occupational exposure to pesticides, herbicides or insecticides and ALS mortality.…”

“…Assignment of specific metals based on a JEM is difficult, as occupational categories are generally too broad to distinguish between exposures to specific metals. Some studies have found an association between occupational exposure to metals and ALS mortality using this methodology,36 although others did not 43. We used the ALOHA+-JEM to assign total metal exposure, which due to the broad categorisation might not have captured possible associations between specific metals and ALS mortality.…”