Cerro de Pasco: last investigation reveals an increase in heavy metals polluttants in the population

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Source International is monitoring population exposure to toxic elements and assessing the environment in and around the mining city of Cerro de Pasco in Peru since 2009.

All our previous studies carried out in Cerro de Pasco have shown the spatial and temporal extension of environmental contamination caused by mining activities and its effects on the community’s health, especially on children.

Between July and August 2021, we carried out an investigation, in collaboration with Centro Labor, local NGO, and Superdotados Peru, peruvian organization.
The recent investigation has focused on an evaluation of exposure biomarkers as heavy metals concentration in hair and intelligence quotient (IQ) in children.

The investigation sites are the community of Paragsha, exposed to mining activities,and the town of Carhuamayo, located 43 kilometers far from Cerro de Pasco, in the neighboring province of Junín. Carhuamayo has been chosen as a control site fornot having active mining activities.


The study evaluated children between 6 and 16 years: a cohort of 81 exposed individuals living in Paragsha (39 boys and 42 girls) and a control group of 17 individuals in Carhuamayo (11 boys and 6 girls) where there are no active extractive activities.

Once again, biomonitoring of hair shows higher levels of heavy metals in the population exposed to mining activities than the control population of Carhuamayo.
The average arsenic level of 0.45 mg/Kg is three times higher than the average value of Carhuamayo (0.15 mg/Kg), lead (4.38 mg/Kg) is six times more than the average level of the unexposed group, and cadmium (0.07 mg/Kg) is double.

If we compare levels of Paragsha with levels fixed by a German laboratory (MicroTraceMinerals), specialized in hair analysis, we observe that the average level of lead in the Paragsha sample is 43 times higher; iron is four times the German limit; manganese seven times; while aluminum is almost four times higher.

Hair heavy metal concentrations increased between 2016-2018 for the Paragsha samples; to following a reduction in levels between 2018-2021. The average concentration of the majority of heavy metals in 2021 is greater than in 2016.

This indicates that sources of pollution are still active and organisms are still exposed to toxic pollutants.


The neurobehavioral study aimed to examine a potential cause-effect relationship between heavy metals human exposure and its effect on psychophysical human health. The Intelligence Quotient (IQ) is a measurement of general intelligence and it is applicabled in mining pollution contexts to qualify and quantify the risk and damage to the psychophysical health of the exposed population since many pollutants,especially heavy metals, released by mining activities have impacts on normal neurological development.
The IQ neurobehavioral study cohort is made up of boys and girls between the ages of 6 and16: the exposed group consists of 81 individuals (39 boys and 42 girls) and the non-exposed group of 17 individuals (11 boys and 6 girls).
The Wechsler Intelligence Scale for Children IV(WISC-IV) was applied, internationally recognizedas the most reliable and widely applicablediagnostic intelligence test, where, individually,each one of the children and adolescents has performed various activities grouped into verbal comprehension scales, working memory,perceptual analysis and information processing speed.

The IQ study, the first to be carried out in the territory of Cerro de Pasco, shows a great difference between the two populations. The average IQ value of the Paragsha sample (CI= 82.5) is 12.3 points lower than the average value of the sample from Carhuamayo (CI =94.8).
In Carhuamayo, 94% of the children have a higher IQ than the national average value set at 82, compared to 59% of Paragsha's sample. In the Paragsha sample, 37% of children and adolescents obtained an IQ in a lower or very low category, compared to international standards.
Although a weak and statistically significant inverse correlation has been identified between hair lead, cadmium, arsenic, manganese, and antimony concentrations and IQ in Paragsha children, higher hair lead levels and lower IQ levels have been measured in Paragsha, the lowest hair lead levels and the highest IQ scores have been measured in Carhuamayo.

This finding is consistent with many previous studies that have reported anassociation between even low blood lead levels and reduced intellectual functioning.

And now?

Our staff is travelling to Cerro de Pasco to share the main findings of the investigation to the communities.

Meetings are planned with local and regional authorities and with Health Dipartment to show how mining activities are severly damaging children's health to push the adoption of urgent measures.

All these data are part of a big database that we are used in the next step: push to A LEGAL CASE.


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