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Heavy metals, a thorn in the flesh

"In toxicology, the right dose differentiates a poison from a remedy"
Photo: Lucía Godínez/EL UNIVERSAL
20/10/2017
18:50
Berenice González Durand
Mexico City
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Romans were among the first civilizations in using Lead (Pb) to build aqueducts and plumbing, yet it is believed that this metal may have contributed to the decline of the empire as lead exposure is linked to lower intelligence, stunted growth, behavioral and learning problems, among a series of other health issues.

Today, Lead (Pb), Mercury (Hg), Cadmium (Cd) and Arsenic (As) are found in foods we consume on a daily basis. In a natural or anthropogenic way, these elements are capable of accumulating in the environment and being transmitted directly to crops or even animals. Moreover, industrialization processes may also contribute to its presence in certain foods.

"There are maximum tolerable values per week in every food," assures Bernardo Lucas Florentino, a specialist in Food Toxicology at the Faculty of Chemistry of the UNAM, adding that these are elements that have been present on the surface of the Earth for thousands of years.

"In toxicology, the right dose differentiates a poison from a remedy."

Nowadays, there are tools that detect metals and that establish their toxicity, such as the Codex Alimentarius Commission, a joint program by the Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO).

Recently, a study by Mexico's National Institute of Public Health (Instituto Nacional de Salud Pública abbreviated INSP) warned of a lead level above the U.S. Food and Drug Administration (FDA) standards in twenty Mexican sweets, such as Tutsi Pop and Rockaletas lollipops, yet lead presence in multiple foods is not new.

"You will find lead in almost any food product, yet lead levels are not as high as they used to be during the eighties when even fuel contained lead."

Mercury, a neurotoxin that affects the central nervous system at certain concentrations, has been integrated into bodies of water where it often contaminates numerous aquatic species in its methylmercury form. This has mainly affected larger species by the process of bioaccumulation.

This phenomenon occurs because the food source for organisms higher on the food chain is progressively more concentrated in mercury, thus magnifying bioaccumulation rates at the top of the food chain meaning that the predatory fish will likely have the highest mercury levels.

"In the last century, in Minamata, Japan, malformations and deaths occurred because their dietary base is marine products and they were contaminated with methylmercury, a substance that is very easily absorbed."

José Belisario Leyva Morales, Ph.D. Specialist in Environmental Chemistry, explains that there are some compounds that are still used in Mexico, despite being prohibited in the U.S. and Europe, such as endosulfan, an off-patent organochlorine insecticide, and acaricide which can cause adverse nervous system effects after long exposure.

According to Leyva Morales, "in Mexico, the problem is that if a product does not comply with the regulations for export, it is usually distributed locally," emphasizing that the health risks remain in the country. 

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