People who are exposed to paint, glue or degreaser fumes at work or on a regular basis may experience memory and thinking problems in retirement or decades after exposure, according to a recent study.

"Our findings are particularly important because exposure to solvents is very common, even in industrialized countries like the United States." Erika L. Sabbath, study author and researcher from the Harvard School of Public Health in Boston, said in a statement. "Solvents pose a real risk to the present and future cognitive health of workers, and as retirement ages go up, the length of time that people are exposed is going up, too."

For the study, researchers examined more than 2,143 retirees from the French national utility company. They assessed their lifetime exposure to chlorinated solvents, petroleum solvents, and benzene, including the timing of last exposure and lifetime dosage. Benzene is used to make plastics, rubber, dye, detergents and other synthetic materials. Chlorinated solvents can be found in dry cleaning solutions, engine cleaners, paint removers and degreasers. Petroleum solvents are used in carpet glue, furniture polishes, paint, paint thinner and varnish.

Of the participants, 26 percent were exposed to benzene, 33 percent to chlorinated solvents and 25 percent to petroleum solvents.

Researchers gave participants eight tests of their memory and thinking skills an average of 10 years after they had retired, when they were an average age of 66. A total of 59 percent of the participants had impairment on one to three of the eight tests; 23 percent had impairment on four or more tests; 18 percent had no impaired scores.

The average lifetime solvent exposure was determined based on historical company records, and the participants were categorized as having no exposure, moderate exposure if they had less than the average and high exposure if they had higher than the average. They were also divided by when the last exposure occurred, with those last exposed from 12 to 30 years prior to the testing considered as recent exposure and those last exposed 31 to 50 years prior considered as more distant exposure.

Based on the findings, people with high, recent exposure to solvents were at greatest risk for memory and thinking deficits.

"The people with high exposure within the last 12 to 30 years showed impairment in almost all areas of memory and thinking, including those not usually associated with solvent exposure," Sabbath said. "But what was really striking was that we also saw some cognitive problems in those who had been highly exposed much longer ago, up to 50 years before testing. This suggests that time may not fully lessen the effect of solvent exposure on some memory and cognitive skills when lifetime exposure is high."

Sabbath said the results may have implications for policies on workplace solvent exposure limits.

The findings were recently published in the journal Neurology.