那么多国家吃了那么多年，哪一个吃出来中国的瘦肉精事故？
http://en.wikipedia.org/wiki/Ractopamine[quote]Regulation around the world
In 27 countries, including Japan, South Korea, Mexico, Taiwan, Canada, the United States, have determined that meat from animals fed ractopamine is safe for human consumption.[5] In the USA, ractopamine is allowed to be used at a feed concentration of 5–20 mg/kg feed for finishing pigs and in dosages of 5–10 mg/kg feed for finishing pigs heavier than 109 kg. In Canada, ractopamine is allowed in meal or pellet feed for finishing barrows, gilts, finishing beef cattle and finishing heavy turkeys (toms and hens) only. The maximum residues limit of ractopamine is 50 ppb and 10 ppb in the USA and Japan, respectively.
In August 2012 Taiwan's legislature passed amendments to the food safety act allowing ractopamine in beef.[6]
Recently, Russia has restricted beef and pork imports to those that are certified free of the additive ractopamine.[[/quote]
Pharmacokinetics in humans
A study was conducted to define the pharmacological response of humans to ractopamine. A single oral dose of 40 mg of ractopamine hydrochloride was given to human volunteers. Ractopamine was rapidly absorbed. The mean blood plasma half-life was around 4 hrs and ractopamine was not detected in plasma 24 hrs after dosing. It was shown that <5% of total ractopamine excreted represented the parent drug, while the urinary metabolites were monoglucuronide and monosulfate conjugates, with ractopamine monosulfate being the major metabolite present.[8]
The metabolic fate of ractopamine hydrochloride is similar in the target species (pigs and cattle), laboratory animals and humans. Besides the pharmacology effect, ractopamine may cause intoxication effect, therefore, any consumption by humans of a meat and/or byproducts of animals that consumed ractopamine with feed for growth stimulation, may result in such clinical effects as tachycardia and other heart rate increases, tremor, headache, muscle spasm, high arterial blood pressure.[9] The effect of ractopamine on humans is not entirely known, but consumption of products that contain ractopamine leftovers is not advisable to people with CVD (cardiovasular diseases).
Human safety
On 6 July 2012, the Codex Alimentarius Commission approved safe limits of residual ractopamine in meats.[10] In the United States, as codified under 21 CFR 556.570, the safe concentrations for total residues of ractopamine hydrochloride are: 0.25 ppm in muscle, 0.75 ppm in liver, and 1.5 ppm in kidney and fat. The acceptable daily intake for total residues of ractopamine is 1.25 micrograms ractopamine hydrochloride per kilogram of body weight per day. The human safety of meat products derived from food animals fed ractopamine has been confirmed by the Joint FAO/WHO Expert Committee on Food Additives (JECFA) in 2004, 2006, and 2010 and by 27 regulatory authorities from around the world.[11][12][13]