Neurotoxicity is as a result of the long term exposure to toxic pollutants, called neurotoxins, which badly affects the central nervous system, or sensory organs. Neurotoxins are chemicals with the ability to damage the nervous system. They do this by destroying the cells that transmit and process signals in the brain. As pollutants, neurotoxins are ever-present in the environment; in schools, homes, road an so on. They are the major sources of environmentalpollution in occupational settings. Production processes in factories are a major environmental pollution source of some of the most harmful neurotoxins. Clinical manifestations of neurotoxicity occur in multiple syndromes and effects, in relation to the nature, level and duration of the exposure. Below are some commonly use chemicals present in the environment that cause central nervous disorders. Their clinical manifestations are identified in this article as well as their relation with toxic exposures. Also precisions about occupational branches and main jobs are involved.

Organic Solvents
Organic solvents are a major source of environmental pollution. This is because it is very common in many sectors of the environment. Millions of workers are exposed this toxic pollutant. They include the printer, spray painter, industrial cleaner, paint or glue manufacturer. The workers in photographic electronic and plastic industries are also victims to this toxic environmental pollutant. Exposure to organic solvents is primarily through skin contact or inhaling fumes of the neurotoxin. Due to its lipophilic and hydrophilic properties, it is able to affect neuronal structures in the brain. The resulting neurotoxic symptoms may include nausea, dizziness, headache, loss of concentration. Long term environmental exposure, particularly in spray painters or microelectronics workers, leads to the development of “Chronic Solvent induced Encephalopathy”, a major nervous system disorder.

Pesticides such as insecticides, fungicides, rodenticides, fumigants and herbicides have been found to exhibits a vast array of chemically diverse structures. Environmental exposure to neurotoxic pesticides is mainly associated with agricultural work. However, other environmental sector workers with substantial risk of being exposed to this environmentally common pollutant include pesticide manufacturing employees, highway and railway workers, as well as greenhouse, forestry and nursery workers.

Research work has found that long term exposure to pesticides increases the risk of Parkinson’s disease by almost 70%. 5% of individuals exposed to pesticides might develop the disease as against 3% for the general population. The onset of pesticide-induced Parkinson's disease appears strongest for exposure to herbicides and insecticides, and after long duration of exposure. Toxicology data suggest that paraquat and rotenone may have neurotoxic actions that potentially play a role in the development of Parkinson’s disease. A recent study show that Parkinson disease was positively associated with group of pesticides that inhibit mitochondrial complex (including rotenone), and a group of pesticides that increase oxidative stress in the brain.

Un-mined lead in the earth’s crust is basically immobile and non-toxic. Once mined and integrated into manufactured products and spread throughout the environment, it is highly toxic. This environmental pollutant is widely used in the production of batteries, metal products (solder and pipes), ammunition and devices to shield X-rays. The neurotoxic effects of lead poisoning on the brain include delayed or reversed development, permanent learning disabilities,seizures, coma and death with severe toxicity.

Manganese is an essential trace metal that is widely used in industry, more commonly used in the manufacture of steel. This places the workers in Manganese, steel and aluminum mining and production industries at risk. Workers in battery production and chemical industries are also at risk. Welders and alloy workers are especially exposed.

Environmental exposure to high levels or chronic low-level of manganese pollution can cause neurotoxicity; the clinical features included psychiatric symptoms. Mood disorders are often observed in workers exposed to manganese pollution. Reports also indicate hallucinations and psychosis, referred to as “manganese madness”. The report also suggests that past exposure to manganese may have lasting consequences on neuropsychiatric symptoms.

Excessive environmental manganese exposure may induce the development of a form of Parkinsonism known as Manganism. Psychiatric manifestations have been reported in cases of manganism. Similarities between the clinical manifestations of Parkinson disease and Manganism may be seen: widespread rigidity, masked faces, speech disturbances and postural instability.  

Neurological occupational diseases have presumably multifactorial etiology, and the environmental health risk after exposure depends on age, sex, genetic factors, socioeconomic and nutritional status, and environmental factors. Even though organic solvents, metals and pesticides have been implicated in neurotoxicity, they represent only a small fraction of the thousands of chemicals in current use that yet to be documented for their neurotoxic effects on humans. Data on environmental exposure of neurotoxins are still insufficient and effects of low-level environmental exposure are difficult to establish, but numerous studies continue to indicate a link between neurotoxin pollution and the onset or progression of central nervous disorders.

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