(AP) -- A Chinese butcher was sentenced to life in prison on Saturday for adding industrial grade nitrates to meat that was blamed in a man's poisoning death,

The harsh sentence handed down to Gao Yanjun reflects authorities' efforts to crackdown on widespread chemical contamination of food and other products that has caused repeated health scares in China and blackened the reputation of the country's exports.

Gao was sentenced Saturday in the northern city of Jinzhou following the death last year of a man surnamed Sun who bought 5 yuan (75 cents) worth of pig intestine at his market stall and then ate it, the official Xinhua News Agency said. Authorities determined Sun had been poisoned. Another man who shared the intestine with Sun was hospitalized in serious condition.

Beginning in 2005, Gao had illegally added industrial nitrate usually used in fertilizer to meat to improve its color and texture, Xinhua said. There was no mention of any other victims.

Four others were sentenced to up to 15 years in prison alongside Gao, Xinhua said.

While industrial nitrates are poisonous, sodium nitrate and nitrite approved for human consumption are commonly added to food as preservatives and color-enhancers. Nitrate-related substances have been reported to cause cancer in animals, but there is no proof they do so in people.

China faces a host of challenges in cleaning up the rampant use of illegal additives and drugs, which are often churned out by makeshift chemical factories, making them particularly hard to trace. Too many agencies oversee food safety, penalties are too light and local officials lack incentives to crack down.

The problems persist despite a crisis in 2008 when six babies died and 300,000 were sickened from drinking infant formula or other dairy tainted with the industrial chemical melamine. The scandal prompted the government to overhaul how it polices food, forming a Cabinet-level food safety commission and passing a comprehensive food safety law.

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