"Everyone in La Oroya is being poisoned by a cocktail of toxic metals such as lead, arsenic, cadmium and other heavy metals," said Fernando Serrano, head of the study group at St. Louis health faculty.

The study showed that 97 percent of children in La Oroya under six have harmful levels of lead in their blood.

Around 18 percent of the children suffer from high arsenic levels in their bodies, and nearly 1 percent have cadmium in their blood.

Executives at The Doe Run Co.'s smelter in Peru's central Andes were not immediately available for comment.

Doe Run Peru says it has spent $78 million on modernization and by 2006 will have invested $94 million in steps to meet government environmental regulations, cutting workers' blood lead levels by a third.

But a recent study by Doe Run and Peru's Health Ministry showed 99.9 percent of children up to age six in La Oroya have abnormally high blood lead levels.

Children have been measured in both studies because they are considered most susceptible to heavy metal poisoning, scientists said.