John McBeth, Talawaan – An ecological disaster looms over North Sulawesi's Minahasa Peninsula. Rampant illegal gold mining is pouring hundreds of tonnes of mercury into the environment. The deadly flow threatens to undermine the economy, contaminate food crops and leave a horrifying health problem for future generations.

Driven by populism and greed, local officials either turn a blind eye to the problem or play an active part in its making. Researchers have identified a police officer as the owner of one of hundreds of crude mills, or trommels, that use mercury to separate gold from ore.

The head of the government's North Sulawesi environmental bureau merely distributes posters showing how to handle mercury, which attacks the central nervous system and causes appalling genetic disorders. Preoccupied with foreign mining firms, Walhi, the country's largest environmental group, pays scant attention to the issue. The one organization that does, tiny Manado-based Yayasan Bina Cipta AquaTech, puts the number of illegal miners in North Sulawesi at 22,000, spread over five or six different sites. Among them are 1,500 working on Australian mining company Aurora Gold's Talawaan gold concession, where more than 100 trommels are in operation. Samples from the Talawaan River – used by residents for domestic purposes and fish-ponds – show mercury levels 70 times higher than the internationally accepted limit for drinking water.

YBCA co-director Inneke Rumengan says miners complain of trembling and stomach and head pains: "They know the mercury is bad for them, but they don't know how bad." Robert Lee, of the overseas-based Wildlife Conservation Society, says miners in parts of the Bone Dumogg National Park are letting mercury-tainted water seep into the Gorantalo city catchment area.

According to the Bureau of Statistics, mercury imports reached 62 tonnes last year, up from five tonnes in 1996. But people familiar with mining and environmental issues say illegal mining consumes as much as 200 tonnes of mercury annually in Talawaan alone.

That compares with the 60 tonnes of methyl mercury dumped between 1920 and the mid-1960s in Minamata, Japan, scene of the world's worst case of mercury contamination. Methyl mercury is more easily absorbed than metallic mercury, but the effects are the same, particularly if trommel operators breath in the toxic fumes during the final burn-off. Says a metallurgist: "They simply have no idea how dangerous that is."

Miners get little reward for their huge risks. They use mercury during initial crushing to extract about 35% of the gold from each 20-kilogram load of ore. When the miner has gone, the trommel owner draws out the rest.