Volatile Organic Compounds and Neurological Disorders: From Exposure to Preventive Interventions

Abstract

A pollutant with the newly established toxic mode is categorized as an emerging environmental contaminant; many point and non-point sources introduce these contaminants in the environment. Volatile organic compounds (VOCs) are the compounds having a low boiling point, variable lipophilicity and volatility, and are being produced from anthropogenic activities and natural sources. With BTEX (Benzene, toluene, ethylbenzene, and xylene) compounds being most abundant (up to 60%), VOCs are used as a reference for the evaluation of VOC exposure and levels in the environment. VOCs may cause behavioral, neurological, dermatological, and respiratory symptoms in humans as evident from experimental and epidemiological data. Humans are exposed to VOCs through skin, GIT, and lungs. Due to the high lipophilicity of VOCs, they can cross biological membranes and the blood–brain barrier (BBB) and thus resulting in numerous neuropsychiatric disorders, comprising of diminished impulsive control, changes in the motor and cognitive functions, hallucinations, headache, dizziness, and dementia. The mechanism of neurotoxicity of single VOC has not been elucidated completely because VOCs are always present as a mixture, but the possible reason may be the oxidative stress and changes in the neurotransmitters and ion channels functions. Several epidemiological and experimental studies (in vivo and in vitro) have been conducted for assessment of neurotoxic mechanism, risk of acute and chronic exposure, and neurobehavioral changes. BTEX compounds are the most toxic environmental pollutants and cause several neuropsychiatric changes including dementia, headache, nausea, malaise, impairment in learning, and memory; toluene is also associated with leukoencephalopathy, fetal solvent syndrome, and sick building syndrome and targets white matter of the brain. Other VOCs having a higher potential of neurotoxicity include solvents containing chlorine, such as trichloroethylene (TCE), perchloroethylene (PERC) and dichloromethylene, formaldehyde, n-hexane and acetone. VOCs’ occupational exposure level in workers is monitored through the measurement of biomarkers; a recent technique for assessment of environmental agents’ exposure is the measurement of micro-RNAs in plasma/serum. Health risks from VOCs are inevitable due to their ubiquitous nature, and measures should be adopted especially in workplaces, urban and industrial areas to keep the level of toxic VOCs below the operational exposure limit (OELs).