In fact, scientists have identified dozens of chemicals that can affect human behavior and cognition, such as lead, mercury, and organophosphates. Although we rarely mention these chemical names, they are ubiquitous in daily life, and people are very easy to come into contact with them. What's particularly frightening is that for children whose brains are developing, exposure to these substances can have a permanent impact on their intelligence.

The topic of brain health has once again become a focal point of concern. After conducting similar research, Philip Grandjean from Harvard University and Philip Landrigan from the Icahn School of Medicine at Mount Sinai in the United States have collectively identified 12 chemicals that pose significant risks to the human brain and are also the most easily encountered. These include:Manganese、Fluoride、Chlorpyrifos、DDT、Tetrachloroethylene (Perchloroethylene)、Polybrominated Diphenyl Ethers (PBDEs)、Arsenic、Lead、Mercury、Toluene、Ethanol、Polychlorinated Biphenyls (PCBs)。

How can we identify these chemicals, and how can we avoid them? Let's understand each one step by step:

○Manganese:
Manganese is widely found in nature, with an average concentration of about 0.25% in soil. It is also present in higher amounts in tea leaves, wheat, and hard-shell fruits. In daily life, manganese is primarily found in dry cell batteries, and it is also present in stainless steel and aluminum cans. In Bangladesh, the levels of manganese in drinking water are relatively high.
This substance has been linked to attention deficit hyperactivity disorder (ADHD) and can affect children's logical thinking and computational abilities.
How to reduce exposure: Minimize the use of dry cell batteries, especially preventing children from biting on them.

○Fluoride:
Fluoride is widely present in natural water bodies, and it is found in various tissues of the human body, but it primarily accumulates in teeth and bones. In daily life, many toothpastes contain fluoride to help prevent tooth decay.
We also frequently encounter fluoride-containing polymers, such as polytetrafluoroethylene (PTFE), commonly known as Teflon. This substance is widely used in surgical implants, for instance, in coronary artery bypass surgeries, and as a substitute for soft tissues in cosmetic and reconstructive surgeries.
It is also the main material for non-stick coatings on cookware.
Philip Landrigan from the Icahn School of Medicine at Mount Sinai conducted a long-term study on 27 Chinese children who had been drinking tap water with excessive fluoride levels. The study found that these children had IQs at least seven points lower than their peers.
How to reduce exposure: Monitor the quality of tap water, and immediately report and stop using it if fluoride levels are found to exceed the standard. When purchasing toothpaste, also try to choose fluoride-free options.

○Chlorpyrifos/DDT:
Chlorpyrifos, more commonly known as Dursban, is a widely used pesticide. It is effective against a variety of chewing and sucking pests on crops such as rice, wheat, cotton, fruit trees, vegetables, and tea plants. However, chlorpyrifos has a long residual life, especially in soil, and is highly toxic to aquatic life, posing long-term adverse effects on aquatic environments.
DDT is another notorious pesticide, which has been banned in many countries and regions. However, due to the lack of an economical and effective alternative for insect control, the World Health Organization announced in 2002 the reintroduction of DDT to control the breeding of mosquitoes and prevent the spread of malaria, dengue fever, yellow fever, and other diseases worldwide.
Both of these pesticides may also be linked to Alzheimer's disease.
How to reduce exposure: To avoid contact with chlorpyrifos, DDT, and other types of pesticides, it is best to soak fruits and vegetables, such as apples, oranges, tomatoes, and chives, in clean water for a few minutes, then rinse thoroughly with running water before consumption.

○Perchloroethylene,:
Also known as tetrachloroethylene or PCE, is an organic compound commonly used as a solvent. It is miscible with most organic solvents such as ethanol and ether. It is widely used in applications like dry cleaning, where it serves as the primary cleaning agent.
In addition to its common use in dry cleaning, perchloroethylene is also utilized in the printing of PCB circuits and in the garment manufacturing industry. It is a key ingredient in automotive cleaning and care products.
Occupations such as nursing, pharmacy, cleaning, hairdressing, and cosmetology often involve exposure to perchloroethylene.
How to reduce exposure: Wear waterproof gloves during the process of dry cleaning clothes and when washing cars to minimize direct contact with perchloroethylene.

○Polybrominated Diphenyl Ethers (PBDEs):
Polybrominated Diphenyl Ethers (PBDEs) are widely used as brominated flame retardants added to many plastic products. However, these substances can easily leach out of products and enter the environment.
Since the 1980s, the levels of PBDEs in the environment have been increasing year by year. The computers we use daily contain a significant amount of PBDEs, as they are present in circuit boards, electronic components, plastic casings, keyboards, and monitors. Every year, hundreds of millions of computers are scrapped, turning into plastic and electronic waste that is recycled or disposed of, with PBDEs accounting for 5% to 30% of the total weight. Most of this electronic waste is shipped to developing countries, including China, where some areas have become collection points for the disassembly of electronic waste, leading to particularly severe PBDE pollution locally.
PBDEs are also widely used in building materials, textiles, and furniture.
PBDEs are neurotoxins, and long-term exposure to these substances before birth can lead to neurological development disorders in children.
How to reduce exposure: In life, it is difficult to avoid contact with plastic products, as well as building materials, textiles, and furniture, which are most likely to contain PBDEs, as are computers. If it is necessary to reduce exposure to PBDEs, experts suggest reducing computer use time, using cloth bags and ceramic products for shopping and storing items, and opting for solid wood furniture whenever possible.

○Arsenic:
Arsenic is a well-known toxic metalloid, infamously known as the main component of "arsenic trioxide," which is referred to as "realgar" in ancient texts. In everyday life, arsenic and its compounds are widely used in dyes, pesticides, herbicides, insecticides, and various types of alloys.
How to reduce exposure: Avoid direct contact with arsenic-containing pesticides and herbicides. If contact is necessary, wear gloves and a mask for protection.

○Lead:
Lead is primarily used in the manufacture of lead-acid batteries, and lead alloys are used for casting type, soldering, and as pigments in gasoline and oil paints. It is also found in children's toys.
Lead and its compounds are highly toxic to humans and can accumulate in the body.
In Oregon, USA, a 4-year-old boy complained daily of stomach pain and vomiting. Initially, doctors thought the child had a viral cold, but blood tests later revealed anemia and an excessively high level of lead in his blood. An investigation of the family's home, which was built in the 1990s, found no lead-based oil paintings or lead-containing paint. Eventually, an X-ray revealed a one-inch long metal piece in the boy's stomach, a toy necklace given to him by his parents. The manufacturer of the necklace subsequently recalled 1.4 million such toys nationwide.
How to reduce exposure: Minimize the use of lead-containing pigments and paints, and buy toys made from natural materials for children, such as wooden building blocks. Prevent children from biting toys, especially small ones or toy parts that they might swallow.

○Mercury:
Mercury, commonly known as quicksilver or water silver, is widely used in various devices such as thermometers, barometers, manometers, sphygmomanometers, float valves, and other instruments. Cinnabar, which is used in traditional Chinese medicine for its supposed properties to ward off illness and evil spirits, is actually mercuric sulfide.
Mercury is also utilized in electronic and electrical products, and mercury vapor is found within the tubes of fluorescent lights. Some cosmetics, such as eye brow dyes, may contain thimerosal, a mercury-containing compound.
How to reduce exposure: Keep children away from household thermometers, and use cosmetics that are mercury-free.

○Toluene:
Toluene is a major product of the petrochemical industry and an important raw material for the organic chemical industry. It is widely used in the production of fine chemicals such as dyes, pharmaceuticals, pesticides, explosives, and fragrances, as well as in the synthetic materials industry. Toluene is an essential material for making nylon and plastic bottles and serves as a solvent in adhesives and dyes.
In daily life, the gasoline we add to our cars contains a significant amount of toluene.
If pregnant women are exposed to toluene over the long term, it can cause problems with the brain development of their offspring and lead to attention deficits.
How to reduce exposure: Store gasoline, pesticides, dyes, etc., in isolated areas and keep them out of children's reach. Wear gloves and masks when handling these substances. Additionally, try to wear less or no synthetic fiber textiles.

○Ethanol:
Ethanol, commonly known as alcohol, is a liquid that can induce a sense of pleasure. In the food industry, ethanol has a wide range of uses, such as in the production of acetic acid, beverages, and flavorings. It is also utilized in the production of many dyes and fuels.
However, ethanol can anesthetize the human nervous system, a fact well known to those who have experienced intoxication. This can cause serious harm to the brain.
How to reduce exposure: Refrain from excessive alcohol consumption and prevent children from drinking alcohol or consuming beverages containing alcohol.

○Polychlorinated Biphenyls (PCBs):
Polychlorinated Biphenyls (PCBs) are chemicals that have been linked to reduced cognitive function in infants and children. They are commonly found in food products, particularly in fish, and can be transferred through breast milk.
PCBs are highly persistent in the environment due to their stability and slow release. They typically enter rivers or coastal waters through industrial wastewater and can be released into the atmosphere through the incineration of materials containing PCBs.
PCBs are highly accumulative within organisms and become concentrated up the food chain. In fish, PCBs can accumulate to levels 200,000 times higher than in the surrounding water, leading to high concentrations in birds and mammals that feed on fish. Scientists have detected these substances in species from penguins in Antarctica to seals in the Arctic.
PCB contamination has become a global issue, as they are found in insulating materials, carbonless copy paper, and engine coolants in our daily lives.
How to reduce exposure: Opt for ocean fish over freshwater and near-sea fish, as the latter tend to have higher levels of PCB accumulation.

These are carriers of neurotoxins:

Manganese
Fluoride
Chlorpyrifos
DDT
Tetrachloroethylene
Polybrominated Diphenyl Ethers (PBDEs)
Arsenic
Lead
Mercury
Toluene
Ethanol
Polychlorinated Biphenyls (PCBs)