Thousands of chemicals need to be re-evaluated for toxicity

According to a new study by scientists, thousands of chemicals need to be re-evaluated for their possible toxicity to human health and the environment.

According to European scientists, conventional tests have underestimated the effect of certain substances accumulated in the 'food chain' (food chain). Among those chemicals are pesticides and possibly pharmaceuticals.

In the article in Science magazine , the team thought that about one-third of the organic substances used in commerce should be re-evaluated for their toxicity. According to the team's estimates, there may be up to 10,000 such substances,

In June, the European Union (EU) Law on Registration, Evaluation, Licensing and Restriction of Chemicals (REACH) began to take effect. According to this law, about 30,000 industrial chemicals will be assessed by the EU about their impact on human health with a total cost of up to 10 billion Euro (13 billion USD).

Bioaccumulation

Some of the chemicals that are capable of bioaccumulation have been used in pesticides.(Photo: BBC)

Substances that remain in the animal's body after eating are called ' bioaccumulative ' or ' persistent ' substances.

Concentrations of these substances will increase during the process of carnivorous organisms. A substance found at a certain concentration in plankton will rise to a higher level in small fish that eat plankton, and will then rise even higher in big fish that eat small fish, and it continues to rise when bears or seals eat big fish .

Twelve types of ' polluting persistent organic substances ' (Pops), including DDT, dioxin and polychlorinated biphenyls (PCBs), have been banned worldwide under the Stockholm Convention (a Pops treaty).

Managers often evaluate the bioaccumulative potential of chemicals through a measure called the octanol / water distribution coefficient (octanol / water partition coefficient - Kow).

Kow is the ratio of the concentration of an octanol and water chemical in equilibrium and at a specific temperature. Basically, it is the ratio between the fat-soluble level and the water-soluble level of a substance. The abundance means that the substance will be released from the body of the fish when it breathes, while calculating the likelihood of fat means that the substance still exists in the fish's body.

This coefficient shows the potential for accumulation of substances during the meat-eating process between fish, snails and plankton.

But the team concludes that there needs to be some other measure to assess the level of bioaccumulation in animals that breathe air. That's Kow: the octanol / air partition coefficient (octanol / air partition coefficient). This factor helps experts determine whether a substance is released through the pleura during respiration.

A food chain - " food chain" of marine life
(Photo: drake.marin.k12.ca.us)

Out of control

The team compared bioaccumulation levels in three food chains of two chemicals: PCB-153 and beta-hexachlorocyclohexane (beta-HCH) - a very close substance to the famous lindane pesticide.

The three lines mentioned above include: plankton - fish; lichen - reindeer - wolf; and adventure creatures - fish - walrus, seals and polar bears.

As a substance with a high Kow, PCB-153 accumulates in all three lines; while beta-HCH, which has a low Kow but has a high Koa, only accumulates in the lichen - reindeer - wolf and marine mammal chains.

Twelve types of ' polluting persistent organic substances ' (Pops) have been banned worldwide under the Stockholm Convention. (Photo: BBC)

According to the team, these bioaccumulation possibilities have been overlooked in conventional tests.

Groups of compounds with a low Kow but high Koa include endosulfan and hexachlorohexane (used as pesticides), musk xylene (a component of perfume and soap) and tetrachlorobenzenes.

Professor Frank Gobas of Simon Fraser University in Burnaby, British Columbia, said: 'About one-third of these organic substances are beyond the control of conventional tests and all have potential for bioaccumulation. learn'.

Professor Gobas argues that it is time for all of these substances to be verified for their toxicity by new measurements of bioaccumulation to know if they are a threat to human health and the environment. .

Quang Thinh