Neurotoxicity refers to any adverse effect on brain function caused by toxic substances or environmental factors. Neurotoxicants are chemicals (such as heavy metals) that have been shown to cause damage to the brain. Environmental toxins include chemical contaminants such as lead, pesticides, radon gas and other radioactive materials.
The term neurotoxicity was first used in 1986 by Dr. William Dement, a professor of psychiatry at Johns Hopkins University School of Medicine. Dement proposed it to describe the observation that the most serious psychiatric illnesses—such as bipolar disorder, major depression, and schizophrenia—often begin with symptoms that are very similar to those caused by poisoning, such as blurred vision, difficulty walking, tingling sensations, and personality changes.
However, not all effects of neurotoxicity are psychiatric in nature. Environmental toxins may also cause physical health problems, such as kidney and liver damage, reproductive disorders, reproductive system malfunction, and cancer.
Neurotoxins can affect the brain through several different routes:
1. They directly attack the brain cells themselves.
2. They interfere with the body’s ability to utilize oxygen and other nutrients properly, a process known as aerobic respiration.
3. They interfere with the transmission of nerve signals, a process called synaptic transmission.
This can result in numerous physical health effects, but also has a variety of serious consequences to the mind.
What are some examples of toxic substances?
1. Lead: A heavy metal that is infamous for causing mental and physical decline in adults and children who are exposed to it on a regular basis.
Symptoms of lead poisoning in adults may include memory loss, headache, nausea, anorexia, depression, and changes in the pulse rate and blood pressure. High levels of lead in the blood may cause coma and death. Children are more susceptible to the damaging effects of lead, which can cause decreased intelligence, behavior problems, hearing and vision problems, and high blood pressure.
2. Mercury: A metal that is used in the manufacture of vaccines as a preservative, and in some types of products, such as thermometers and batteries.
The effects of high levels of mercury in the body are similar to those of lead.
3. Pesticides: Pesticides come in many different forms.
The most common class of pesticides is known as organophosphates, which were first developed as nerve gases. They interfere with the function of the neurotransmitter acetylcholine and are commonly found in products such as insect sprays, fertilizers, and flea and tick collars for pets. At very high levels, they have the potential to cause massive damage to the nervous system and death.
Other types of pesticides can affect mental health in various ways.
4. PCBs: Polychlorinated biphenyls are a group of chemicals that were commonly used in electrical equipment and as insulators in buildings, until they were banned due to health and environmental hazards.
They may cause a wide range of problems, including psychiatric effects such as depression, anxiety, and phobias. They may also affect the immune system and cause cancer.
5. Carbon Monoxide: A colorless, odorless, highly poisonous gas that is a by-product of the incomplete combustion of fossil fuels and can be found in car exhausts and plain old smoke.
It is especially dangerous for people with heart or lung conditions, as it can rapidly uptake blood to the point where it is lethal.
Research shows that toxic substances can affect people’s mood by altering their brain chemical balances.
- Animal models of manganese’s neurotoxicity (N Manganese – Neurotoxicology, 1999 – researchgate.net)
- Cyclosporine neurotoxicity: a review (JMM Gijtenbeek, MJ Van den Bent, CJ Vecht – Journal of neurology, 1999 – elibrary.ru)
- Ionic dependence of glutamate neurotoxicity (DW Choi – Journal of Neuroscience, 1987 – Soc Neuroscience)
- Manganese neurotoxicity (AW Dobson, KM Erikson, M Aschner – ANNALS-NEW YORK …, 2004 – libres.uncg.edu)
- Nitric oxide neurotoxicity (VL Dawson, TM Dawson – Journal of chemical neuroanatomy, 1996 – Elsevier)
- Glucose neurotoxicity (DR Tomlinson, NJ Gardiner – Nature Reviews Neuroscience, 2008 – nature.com)