Occupational Solvent Exposure and Brain Function: An fMRI Study

Abstract

Background: Deficits in cognitive function have been demonstrated among workers chronically exposed to solvents, but the neural basis for these deficits has not been shown.Objectives: We used functional magnetic resonance imaging (fMRI) to compare pathophysiological changes in brain function between solvent-exposed and control workers.Methods: Painters, drywall tapers, and carpenters were recruited from the International Union of Painters and Allied Trades, District Council 9 in New York City and District Council 21 in Philadelphia, Pennsylvania, and from the Carpenters Union in New Jersey. Twenty-seven solvent-exposed and 27 control subjects of similar age, education, and occupational status completed the N-Back working memory test during fMRI. After controlling for confounders (age; lifetime marijuana, cocaine, and alcohol use; blood lead; symptoms of depression; verbal intelligence), voxelwise group analysis and regional activation levels were compared and then correlated with an index of lifetime solvent exposure.Results: Solvent-exposed workers’ performance on the N-Back was significantly worse than that of controls. Activation of the anterior cingulate, prefrontal, and parietal cortices—areas serving working memory function and attention—was also significantly lower for solvent-exposed workers relative to controls. After controlling for confounders, we observed a negative correlation between lifetime solvent exposure and activation in these same regions among the solvent-exposed workers.Conclusions: This study is one of the few to document neural structures affected by exposure to solvents. Our findings provide a biological mechanism for the neurobehavioral deficits in working memory and attention that have previously been reported by other groups studying the effects of chronic exposure to solvents. These imaging markers, which are consistent with the neurobehavioral measures in our subject population, are consistent with altered brain pathology caused by prolonged exposure to solvent mixtures during construction work.

Effect of Prenatal Organic Solvent Exposure on Structural Connectivity at Childhood

“…These results are appeared to be in line with studies reported association between prenatal exposures to organic solvents in general and neurocognitive deficits [1,6,[9][10][11][12]. We also observed the same affected regions than the ones found for adults chronically highly exposed to solvents [24]. Moreover, in this study, children whose mothers had high levels of EEAA exhibited higher fiber density between two pairs of regions.…”

Occupational Exposure to Solvents: Neuropsychiatric and Imaging Features

“…A study utilizing functional MRI (fMRI) compared activations during a working memory task (N-back, sequence of letters) in asymptomatic solvent exposed industrial painters (N527) and unexposed workers from other building trades (N527). 8 Exclusion criteria included psychiatric disorders, current medications, and presence of white matter abnormalities on T2 MRI. The exposed group performed more slowly (reaction time during the 0-back condition) and less accurately (fewer correct hits, more false hits) than the unexposed group.…”

“…A functional magnetic resonance imaging (fMRI) study that compared construction workers with occupational chronic solvent exposure to matched (age, education, occupational status) construction workers without solvent exposure during completion of a working memory task reported differences in both performance and regional brain activations. 8 Subjects viewed a visual sequence of numbers and pressed a button when a target letter was identified (N-back task, matching to 0, 1, 2, or 3 back in the sequence, depending upon instructions). Left: Approximations of areas activated across groups by the N-back task (purple) and the areas in which the exposed group had lower activation (blue) after correction for verbal IQ and lead exposure are illustrated on coronal (top) and axial (bottom) MRIs.…”

Time after Time: Environmental Influences on the Aging Brain

“…But because the neurological disorders with which they are linked mirror those associated with motor and sensory-function declines of aging, they can be mistaken in diagnosis for the effects of aging or diseases of old age like Parkinson’s and Alzheimer’s diseases. 22 , 25 , 26 It also appears that long-term nonacute exposures to solvents and pesticides can affect verbal memory, attention, and spatial skills, with effects that may not become apparent until later in life, when they, too, might be confused with or compounded by aging-related conditions 22 , 27 …”