右。 美国EPA规定在1000ng/m3的浓度下不超过8小时,这是很保守的规定。况且新的标准公布需要若干年,没人愿意冒险。就像Arsenic in drinking water的规定,从50 ug/L降
到10ug/L用好几年的时间,直到有几个小孩得白血病。从前大家说吃鱼好,现在EPA建议育龄妇女每周吃鱼不超过4oz (112g)。就是因为mercury content in farm raised fish is extremely high (especially in big fish: salmon, tuna,shark,etc.)
If mercury is not a big problem EPA won't spend huge amount of money on mercury study every year for the last ten year.