The centuries-old silver mines of Mexico are even today lethal traps of toxic mercury. Workers who helped recover mercury and silver from the over 400-year mine waste from around a dozen old Spanish mining towns, have been afflicted with health problems. Yet, sadly, no comprehensive study has been conducted to date on the toxic effects of mercury from these mines. Some, who live and work around the old mines, say there's no doubt it is still deadly.

In the flourishing silver mining activity that took place in Mexico between 1550 and 1820, millions of kilogrammes (kg) of mercury was used to extract silver and remains buried even centuries later at dozens of sites, including the shallow waters of El Pedernalillo Lake. And it continues to pose a serious risk to the residents of these areas.

It is an established fact that Spain had sent 50,000 tonnes of mercury to Mexico during the colonial period. The Spaniard miners mixed about two kg of mercury with the ore to obtain about 500 grammes of silver. The mercury was then burned off or released into the ground. "Amazingly, it's still there after almost 400 years,' says Evan Lloyd, spokesperson for the environmental cooperation commission of Mexico, Canada and the us. In October, the commission released a map of 66 "mercury hotspots' around Mexico