Huancavelica’s Toxic Legacy: Mercury, Arsenic, and Lead Exposure
Perched high in the Peruvian Andes, Huancavelica carries one of the heaviest toxic burdens in the world. For centuries, this small city was the primary source of mercury for refining silver in the Andes. From 1564 until large-scale production finally ceased in 1975, an estimated 25,000 metric tons of mercury vapor escaped into the environment. Refining also released arsenic and lead, leaving behind a noxious legacy that still affects every corner of the community.
Today, Huancavelica’s population of approximately 50,000 residents shoulders this toxic burden on a daily basis, and about 18,000 are at risk of mercury, lead and arsenic exposure inside of their homes.
Almost 43% of the houses in the city are constructed of adobe made from local, contaminated soil. Our research has demonstrated that these homes contain levels of these heavy metals above screening levels. In addition, there is off gassing of elemental mercury from the walls of many of these homes. Residents are exposed to these toxins through ingestion of particle-bound heavy metals released from the walls and floors as dust, and through inhalation of mercury vapors.
Mercury’s toxic effects are particularly devastating for pregnant and lactating women, fetuses, and children. Chronic exposure to mercury vapor can increase the risk of spontaneous abortion, stillbirth, and birth deformities—often without any outward signs of illness. After birth, exposure can continue through breast milk.
Children are especially vulnerable. Their developing brains and nervous systems are more easily harmed by heavy metals, and their frequent hand-to-mouth behavior increases exposure. In Huancavelica, nearly every household in our studies includes children or infants.
The Health Effects
Mercury Poisoning – Persistent and sometimes irreversible neuropsychological damage, including personality changes, irritability, depression, anxiety, obsessive-compulsive behaviors, memory loss, and difficulty concentrating. Physical effects may include tremors, loss of appetite and muscle control, speech impairment, anemia, excessive salivation, gum disease, and gum discoloration.
Arsenic Poisoning – Lowered red and white blood cell counts, irregular heartbeat, vascular damage, kidney injury, increased cancer risk, and—like mercury—birth deformities and toxin transfer through breast milk.
Lead Poisoning – Damage to the central nervous system and kidneys, spontaneous abortions, reduced birth weights, and developmental delays. Even at low levels, lead can harm children’s cognitive and physical growth.
A Community Living With Invisible Danger
Huancavelica is not just historically significant—it is one of the most mercury-contaminated urban areas in the world. Here, environmental contamination is not a relic of the past but a present, daily reality. Every breath and every step inside these homes carries an invisible risk.
The challenge is immense, but so is the need for urgent action. Addressing this contamination is not just an environmental necessity—it is a matter of protecting human health, safeguarding children’s futures, and breaking the cycle of toxic exposure that has persisted for generations.
Centuries of historic mercury processing have left Huancavelica, Peru, with one of the highest rates of household contamination in the world. Sampling shows that 75% of earthen homes have mercury (Hg) levels in their walls, floors, or indoor air that exceed health-based screening limits.
Given that about 40% of the city’s homes are earthen, an estimated 18,000 residents, many of them children, may be at risk of serious mercury exposure and long-term health effects.
2015 Pilot Study
In 2015, the Environmental Health Council (EHC) and our local partner, Asociación Nuevavelica, conducted a pilot study to test whether sealing mercury-contaminated walls and floors could make homes in Huancavelica safer. Six earthen homes were selected for treatment, and six additional homes were monitored without treatment for comparison.
The study’s goal was to evaluate the encapsulation method—installing concrete floors and plaster or cement walls—to determine if it could effectively reduce residents’ exposure to mercury (Hg) and other heavy metals.
Key Findings
Conclusions and Recommendations
Health-Based Screening Levels
Ingestion Pathway
Inhalation Pathway
Based on RI results, three out of every four earthen homes in Huancavelica are contaminated above these safety thresholds—placing thousands of families at daily risk of neurological damage, developmental delays in children, and other mercury-related health effects.
This is not a distant problem. It is an urgent public health crisis that demands action to protect Huancavelica’s most vulnerable residents—especially its children.
Our work is grounded in years of scientific research in the city, which has involved the collection and analysis of hundreds of soil, dust, and air samples from study participants’ adobe homes and public spaces.
Please help us achieve our mission!
The Environmental Health Council is a 501(c)3 organization, and donations are tax-deductible. The EHC does not charge an “overhead” and all donations are dedicated to research, assessment, public and community outreach and organization, and remediation/demonstration project.
By fractionalizing the problem, we not only make remediation more manageable, we also make it possible for supporters to see exactly how their contribution changes lives. Each room restored is a step toward breaking the cycle of toxic exposure and creating a safer future for Huancavelica’s children.
