Exposure to petroleum-based lubricants work associated with MS risk

People exposed to petroleum-based lubricants at work had 38 per cent higher odds of multiple sclerosis (MS), a study has found.

The research examined exposure to engine oil, hydraulic oil and cutting fluids used to cool or lubricate metal during metalworking.

The association was stronger among current smokers and people lacking a genetic variant linked to lower MS risk, although the findings do not establish that these substances cause the condition.

Anna Karin Hedström, study author at Karolinska Institutet in Stockholm, said earlier research had linked MS to substances that irritate the lungs.

She said: “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.

“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.”

Researchers analysed data from 2,872 people with newly diagnosed MS and 6,122 people without the condition in Sweden.

Participants had an average age of 35 and were matched by age, sex and residential area.

MS is a chronic neurological condition in which the immune system attacks the brain, spinal cord and optic nerves.

Both genetic and environmental factors have previously been associated with an increased risk of developing the condition.

Participants completed questionnaires about their employment histories and possible exposure to cutting lubricants and fluids, engine oil, hydraulic oil and concrete form oil.

Researchers classified participants as occupationally exposed if they had encountered at least one of these substances before the year in which their first MS symptoms appeared.

Common occupations involving exposure included metalworking, construction, automotive repair and machinery maintenance.

Among people with MS, 251 participants, or 8.7 per cent, reported workplace exposure to petroleum-derived lubricants.

This compared with 399 people, or 6.5 per cent, in the group without MS.

After adjusting for age, sex, residential area, smoking and other factors, researchers found that exposed participants had 38 per cent higher odds of MS than those reporting no exposure.

Longer and greater exposure were also associated with higher odds.

Each additional year of exposure was linked to a 2 per cent increase in the odds of MS, as was each additional hour of exposure per week.

Higher overall amounts of exposure were also associated with increased odds.

Because biological changes associated with MS may begin years before symptoms appear, researchers repeated the analysis using only participants exposed at least seven years before their first symptoms.

The association remained, with exposed participants having 55 per cent higher odds of MS.

The researchers also examined whether smoking and genetic differences affected the association.

Genetic information was available for a smaller group of participants.

Among those exposed to petroleum-based lubricants, smokers had higher odds of MS than would be expected from simply adding the separate effects of smoking and lubricant exposure.

A similar pattern was found among people who lacked a genetic variant associated with lower MS risk.

The analysis also considered combinations of risk factors.

Participants who had been exposed to lubricants, smoked, carried a genetic variant linked to higher MS risk and lacked a variant linked to lower risk had more than 33 times the odds of MS compared with people who had none of these factors.

However, only 16 people with MS and two without the condition fell into this group, making the estimate less precise.

The findings suggest that smoking and genetic susceptibility may influence the association between workplace lubricant exposure and MS, but they do not establish a causal relationship.

Hedström said the results warranted further investigation.

“These findings point to the need for a closer look at workplace exposures that may play a role in MS risk,” she said.

“Future studies should gather more detailed information about when people were exposed to these lubricants and how much they were exposed to at work.”

The study had several limitations, including its reliance on participants’ recollections of workplace exposure.

Some may have incorrectly remembered or classified the substances they encountered, while other occupational exposures could also have influenced the results.

The researchers said further studies in different populations are needed to confirm the associations.