A large new study finds that exposure to common industrial solvents on the job is associated with reduced cognitive performance, especially in men.
Key findings show:
- Men exposed to solvents like gasoline, trichlorethylene, white spirit or cellulosic thinners performed worse on tests of memory, processing speed and executive function.
- The more types of solvents men were exposed to and the longer the exposure time, the greater the cognitive decline.
- Effects were seen even after adjusting for socioeconomic factors, health issues, and hazardous working conditions like night shifts and noise.
- This is the first large study to also find cognitive impacts from solvents in women workers.
Source: Open Environ Med. 2020
The research, published in Occupational & Environmental Medicine, used data on nearly 42,000 middle-aged adults from the French CONSTANCES cohort study.
It adds to growing evidence that solvents may harm brain function.
While many safety measures exist today, millions of workers continue using these chemicals daily.
The cognitive declines were found before any dementia symptoms arose, suggesting a need for even stronger protections and interventions.
Widespread Solvent Exposures Among Working Adults
Organic solvents are found in many workplace situations and products worldwide.
Their uses include:
- Degreasing machines and tools
- Thinning paints and varnishes
- Cleaning electronics
- Dry cleaning fabrics
- Producing pharmaceuticals
Common examples include trichloroethylene, mineral spirits, benzene, toluene, n-hexane, and more.
Past studies estimate 8% or more of workers in industrialized nations handle solvents regularly.
These exposures are concerning because many popular solvents are now known neurotoxins.
They can dissolve fatty tissues surrounding neurons in the brain.
Animal and human studies have already linked heavy or prolonged solvent use to effects like:
- Headaches, fatigue and dizziness
- Impaired concentration, memory and reaction time
- Personality and mood changes
However, most prior research studied those with workplace accidents or very high exposure levels.
The new French data looks at lower everyday exposures in a general population.
Poorer Cognitive Scores Linked to Solvent Use
The researchers analyzed data from the CONSTANCES study, an ongoing health project sampling French adults aged 18-69.
Over 200,000 working and retired adults have enrolled since 2012.
All participants take cognitive tests covering areas like memory, processing speed and executive function.
The 41,854 people included also completed surveys about their lifetime job history and solvent use.
16.8% of male participants reported occupational solvent exposure, compared to just 2.5% of females.
The study found men exposed to any of 4 common solvents – gasoline, trichloroethylene, white spirit or cellulosic thinners – performed worse on cognitive tests.
This held true after adjusting for age, socioeconomic status, lifestyle risks like smoking, and chronic health issues.
Those using multiple solvent types showed a clear dose-response, with higher risk as more solvents were involved. The association also rose with longer total years working with solvents.
And notably, the effects were strongest for those currently exposed versus no longer exposed.
This suggests the impacts may be at least partly reversible after ending contact.
While less women reported solvent use, those exposed also showed lower cognitive functioning.
In particular, white spirit exposure was linked to poorer scores.
Working Conditions May Play an Added Role
An important aspect of this study was looking at how hazardous workplace conditions interact with solvent exposures.
Jobs with frequent solvent use also often involve other risks like night shift work, loud noise, and repetitive tasks.
When adjusting for these other factors, the association between solvents and cognition dropped but remained.
This highlights that solvents impact brain function above and beyond other work stresses.
However, the interaction also shows that eliminating solvents alone cannot remove all cognitive threats on the job.
Workplaces overall need to prioritize reforms that support employee cognitive health and safety.
Potential Mechanisms for Solvent-Related Cognitive Decline
Research continues investigating exactly how solvent fumes impair cognition. Possible mechanisms include:
- Inflammation and reduced blood flow in the brain due to irritants entering the lungs and bloodstream.
- Direct damage to myelin and neurons from lipids in the solvents dissolving insulating sheaths.
- Imbalances in neurotransmitters like dopamine and serotonin that regulate memory, mood, and motivation.
- Oxidative stress from reactive solvent byproducts harming cellular structures.
- Autoimmune reactions triggered by abnormal proteins created after solvent exposure.
- Epigenetic changes like DNA methylation silencing genes involved in memory and learning.
Whatever the processes involved, it seems even low or moderate solvent amounts can gradually take a toll.
Patients also rarely associate “normal” workplace exposures with nervous system issues.
Continuing risks decades later point to possibly permanent changes too.
More research on underlying mechanisms will help identify who is most vulnerable and how best to detect early damage.
Health Effects & Cognitive Deficits from Solvents
This study focused on adults aged 45-69, before any dementia diagnosis.
But lower cognitive scores may have wide-ranging impacts throughout life, including:
- Poorer job performance and work safety issues
- Increased mental health problems like depression
- Reduced quality of life and independence
- Higher likelihood of mild cognitive impairment and future dementia
So while solvents may not directly cause diseases like Alzheimer’s, they may hasten their development or worsen their progression.
Catching subtler changes from solvents also allows earlier intervention to slow further damage.
Cognition tests like those used here can identify declines well before they interfere with daily living.
Workers should have regular medical monitoring that includes detailed cognitive screening.
More Protection Needed for Workers Using Solvents
Occupational health policies have improved greatly over past decades.
But this study highlights that better protections are still needed globally.
Important steps going forward include:
- Expanding education on solvent risks, safe handling and PPE
- Increasing ventilation, automation and safer alternative products
- Regularly monitoring workers for early cognitive changes
- Lowering permissible exposure limits for solvents
- Providing cognitive screening tools to primary care doctors
- Extending solvent exposure assessments to include office roles
- Creating financial incentives for firms to reduce solvent reliance
On an individual level, workers can also reduce their risk by carefully following safety protocols, wearing respirators when required, and supporting company initiatives to use safer chemicals.
While more research is still needed, the mounting evidence leaves little doubt solvents impair cognitive function.
Companies and regulators must make brain health a priority in all workplaces that handle these chemicals.
And doctors should be vigilant about cognitive declines in any patient with solvent exposure history.
References
- Study: Associations between occupational solvent exposure and cognitive performance in the French CONSTANCES study
- Authors: Noemie Letellier et al. (2020)
