Workplace Lubricants: An Overlooked MS Risk Factor?

Occupational exposure to petroleum-based lubricants, including engine oil or hydraulic oil, is linked to an increased risk of developing multiple sclerosis (MS), particularly among smokers and those with certain genetic risk factors.In a population-based study of nearly 2900 patients with newly diagnosed MS and more than 6100 control individuals, 8.7% of those with MS reported workplace exposure to petroleum-based lubricants compared with 6.5% of control individuals.After adjusting for smoking and other potential confounding factors, the investigators found that workplace exposure to petroleum-based lubricants was associated with a 38% increased risk of developing MS compared to control individuals. This association was particularly pronounced among smokers and those with specific genetic factors.The risk of developing MS also increased with more years of exposure and greater weekly exposure hours.Common occupations among those reporting exposure included metalworkers, construction, automotive repair, and machinery maintenance.“Previous research has linked lung irritants such as cigarette smoke, organic solvents, and air pollution to MS risk, but petroleum-derived lubricants have not been closely studied,” lead investigator Anna Karin Hedström, MD, PhD, of Karolinska Institutet in Stockholm, Sweden, said in a statement.“Our findings suggest that exposure to these products in the workplace, which is common in industrial settings, is associated with higher odds of MS, especially when combined with smoking or certain genetic characteristics.”The study was published online on November 4 in Neurology.The Risk for MS at WorkMS is a chronic disease that is shaped by genetic and environmental factors, such as Epstein-Barr virus infection, smoking, adolescent obesity, limited sunlight exposure, and occupational exposure to organic solvents.Petroleum-based lubricants, including cutting fluids, engine oil, hydraulic oil, and concrete form oil, are commonly used in industrial settings. Workers can inhale airborne droplets and mists or come into contact with these substances on a daily basis. However, whether there is a link between these lubricants and MS is unknown.To determine whether workplace exposure to such lubricants was associated with MS and whether smoking or specific human leukocyte antigen (HLA) genotypes influence the association, researchers examined data from 2872 patients with newly diagnosed MS and 6122 control individuals in Sweden between 2005 and 2015.Participants were matched by age, sex, and residential area. In both groups, the mean age was 34.6 years, women accounted for 72% of the study population, and most participants were of Nordic ancestry.MS diagnoses were confirmed by a neurologist using the McDonald criteria.Participants completed questionnaires about their work histories and exposure to cutting fluids, engine oil, hydraulic oil, and concrete form oil. Exposure was defined as workplace contact with at least one of these substances before the year in which their first MS symptom appeared.Smoking, Genes, and the Risk for MSA total of 251 patients with MS (8.7%) and 399 control individuals (6.5%) reported workplace exposure to petroleum-based lubricants.Overall, exposure to lubricants was linked to a 38% higher odds of MS, after adjusting for age, sex, residential area, ancestry, history of infectious mononucleosis, BMI at age 20, and smoking. The association was similar in women (odds ratio [OR], 1.46) and men (OR, 1.40).The most common occupations among those reporting exposure to lubricants were metalworking (23%), construction (17%), automotive repair (11%), and machinery maintenance (10%).Each additional year of exposure and each additional hour of exposure per week, were independently associated with a 2% higher odds of MS.When researchers examined individual lubricants, significant associations with MS were found for cutting fluids (OR, 1.45), engine oil (OR, 1.30), and concrete form oil (OR, 1.92) but not hydraulic oil.Smoking further strengthened the association. Compared with nonsmokers with no lubricant exposure, those who smoked and reported exposure were 2.5 times more likely to develop MS. The combined association was greater than the effect of either exposure alone.Genetic analyses showed that the link between lubricant exposure and MS was stronger among those without HLA-A*02:01, an allele associated with a reduced risk for MS. A similar pattern was observed among carriers of HLA-DRB*115:01, an allele associated with an increased risk for MS, although this finding was not statistically significant.Participants who smoked, reported occupational exposure to lubricants, carried the MS risk allele HLA-DRB1*15:01, and lacked the protective allele HLA-A*02:01 had more than 33 times the risk of developing MS compared with those without these risk factors. However, this was based on just 16 participants with MS and two control individuals.The association between lubricant exposure and MS remained even after researchers excluded exposures reported within 7 years before the first symptoms appeared (OR, 1.55).When Does MS Begin?Knowing when environmental exposures occur and how they may contribute to the risk for MS remains a challenge, Ruth Ann Marrie, MD, PhD, of Dalhousie University in Halifax, Nova Scotia, Canada, wrote in an accompanying editorial. She was not involved in the research.“Growing epidemiologic and biological evidence suggests that MS may begin years before typical symptoms such as optic neuritis, present,” Marrie noted.Changes associated with MS may begin years before typical symptoms develop, which makes it difficult to determine whether an exposure occurred before or after disease onset, she added.Self-reported exposure is another important consideration because workers may be exposed to multiple substances on the job, making it difficult to determine whether petroleum-derived lubricants alone contributed to the risk for MS.“Residual confounding because of other occupational exposures likely persists,” Marrie wrote.It remains unclear “whether the relevant periods vary by risk factor or whether the sequence of risk factor exposures matters,” Marrie wrote. She also called for “a feasible means of accurately identifying the onset of the biologic and prodromal phases of the disease” to help researchers better understand when environmental exposures may contribute to MS.Disclosure information for study authors is available in the original study publication. Marrie reported receiving research funding from Canadian Institutes of Health Research, MS Canada, the National Multiple Sclerosis Society, and other organizations, and serving as a coinvestigator on studies funded by Biogen Idec and Roche Canada.