Link between solvent-based parts washers and damage to the nervous system
Synopsis of article published in The Lancet April 26, 1997
Occupational Medicine section:
Solvents and Neurotoxicity
By R. F. White & S. P. Proctor
Summary: Close to ten million Americans are exposed to solvents on a daily basis, many of that number through solvent-based parts washers. Medical studies such as the one digested here find growing evidence that long-term exposure to such solvents through breathing and skin contact can produce depression, confusion, attention deficit, memory loss, irritability and fatigue. Physical symptoms may include tingling, numbness, loss of smell and muscle weakness. These symptoms may be irreversible. Often they occur in workers who are not obviously or clinically ill. Primary prevention of these disorders is essential because early diagnosis is difficult and treatment options are limited.
Authors: R.F. White and S.P. Proctor, Neurology Department, Boston University School of Medicine, Department of Environmental Health, Boston University School of Public Health and Boston Environmental Hazards Center.
Doctors are finding an increasing number of health problems associated with solvent exposure. Nearly 49 million metric tons of solvents are produced each year in the United States and more than 9.8 million Americans are in daily contact with those solvents. Symptoms are generally linked to the central nervous system (CNS) or the peripheral nervous system (PNS). Often these symptoms go away after the patient is removed from the toxic environment, but long term exposure can produce longer-lasting or even permanent effects including cognitive and behavioral changes.
There are many kinds of organic solvents but the solvents of concern in this study are liquids volatile at room temperature such as mineral spirits. They are usually absorbed through inhalation and/or skin contact and build up in fatty tissue.
Industries which expose workers to these solvents include automotive manufacturing and repair, paint and varnish manufacturing and application, the electronics industry, metal degreasing and parts cleaning in common industrial machinery maintenance.
Over the past 25 years, numerous studies have documented the neurotoxicity of solvents. This toxicity has been demonstrated by neurophysiological methods like motor and sensory examination of the central and peripheral nervous systems with MRI, Computed Tomography, SPECT, Electromyelogram, evoked potentials, nerve conduction and reflex testing.
More recently, this toxicity has also been demonstrated by a growing number of studies employing neuropsychological assessment techniques of cognitive function, motor function and mood and personality aberrations– techniques like questionnaires, written tests and interviews.
One important result of this new line of study is the discovery that, as more workers are screened using these methods, there is growing evidence that many workers are suffering serious symptoms without being obviously or clinically ‘ill’. Scientists and clinicians are now discovering the magnitude of a problem that was previously below their radar.
Many people experiencing nervous system effects of solvent exposure are aware their symptoms are related to use of organic solvents, but most are not.
The new methods of neuropsychological testing can be helpful in identifying the effects of acute or chronic solvent exposure. Acute, low-dose exposures can be measured by test results that show marked improvement after the exposure is eliminated. However, chronic exposure often shows permanent changes in such functions as attention span, the ability to deploy strategies for problem solving, response to novel stimuli, short term memory and mood/affect. Some patients with solvent exposures exhibit cognitive disorders such as post-traumatic stress disorder, depressive disorder and motivational disorders such as malingering or sick-role playing.
It must be understood that recommended limits of exposure published by government and other authorities are no guarantee of safety. Chronic, long-term exposure at levels below the recommended standards has produced evidence of nervous-system dysfunction.
Treatment options for patients with solvent exposure disorders are limited. The first step is to remove the patient from contact with solvents. Treatment then focuses on alleviation of symptoms such as headache or dizziness. Antidepressants or stimulant treatments can be effective in improving arousal and motivation. If the patient has a post-traumatic stress disorder, psychotherapy, anxiolytic treatment or a combination is indicated.
Because early diagnosis is difficult in most clinical settings and because treatment options are limited in number and effectiveness, it is essential that industry and public health authorities focus on primary prevention of long-term exposure to volatile solvents.