Mercury in fish
鱼之毒

Hold the sushi
寿司且慢用

Aug 27th 2009 | NEW YORK
From The Economist print edition

A pollution trail from the streams to the ocean
百川入海，污染相伴

HERBERT HOOVER once described fishing as a “discipline in equality—for all men are equal before fish”. The converse, unfortunately, is not true. After the release of a new government study that documents the prevalence of mercury in freshwater fish, American consumers are aware that all fish are not equal, or at least not equally good to consume.
赫伯特•胡佛（Herbert Hoover）曾把钓鱼称为一项“公平的运动——因为在鱼类面前，人人平等”。不幸的是，反过来情况并非如此。据一项新的政府研究结果记录，淡水鱼中普遍含有汞的成分。此项研究发表后，美国消费者才认识到，在人类面前，鱼和鱼并不平等，或者至少吃鱼的时候，不能等而视之。

The new study was conducted by the US Geological Survey (USGS), a scientific agency run by the government. It found traces of methylmercury, a form of mercury that is readily absorbed, in every fish sampled in 291 streams across the country. In around a quarter of those fish, the amount of mercury was above the level set by the Environmental Protection Agency (EPA) as safe for human consumption. Mercury levels at more than two-thirds of the sites exceeded what scientists believe fish-eating mammals, such as mink and otters, should ingest.
从事这项新研究的，是由政府管理的科研机构——美国地质调查局（US Geological Survey，简称USGS）。研究发现，采自全国291条河流的鱼样中，都含有一种易被人体吸收的汞——甲基汞。四分之一的鱼样本中，汞含量超过了由环境保护局（Environmental Protection Agency，简称EPA）设立的人类食用安全标准。三分之二选本中汞含量超过了科学家们认为水貂、水獭等以鱼为食的哺乳动物可摄入的含量。

The leading source of mercury is pollution from coal-burning power plants, which accounts for 40% of all domestic anthropogenic mercury, according to the EPA. It is emitted through smokestacks and deposited in rain and snow, often making its way into the water. Mercury can be toxic, and adult exposure to it can lead to reproductive problems, memory loss and tremors. Prenatal and infant exposure can cause mental retardation, deafness and blindness. The National Research Council, an organisation that looks at science and public policy, estimates that more than 60,000 children are born each year at risk of learning disabilities because they have been exposed to methylmercury in the womb.
据环保局统计，汞的主要来源是占国内人为排汞量40%的燃煤电厂污染物。烟囱排放及雨雪沉积后，汞常常进入水中。汞有毒，成人接触汞可能导致生殖障碍，记忆力减退，身体颤抖。胎儿及新生儿接触汞会造成智障，耳聋，失明。研究科学和公共政策的组织，国家研究委员会（The National Research Council）估计，因为在母体子宫中接触过甲基汞，每年出生的儿童中有6万多可能出现学习障碍。

The fish lobby points out that the USGS findings do not necessarily damn the commercial fish industry, as most of the fish people eat comes from the ocean and not from freshwater streams. But mercury levels are high in marine fish, too—particularly in larger species, such as shark, tuna and swordfish. Mercury accumulates as it works its way up the food chain. A report released earlier this year by Harvard and the USGS forecasts that mercury levels in the Pacific Ocean will rise by 50% by 2050 as emissions from coal-fired power plants increase.
为鱼辩护者指出，美国地质调查局不必迁怒到商品鱼业，因为人们所吃的鱼多是产自海里，而不是来自淡水河。但是，海洋鱼类中的汞含量也很高——尤其在体型较大的鱼类体内，如鲨鱼，金枪鱼和箭鱼。本年初，由哈佛大学及美国地质调查局发布的报告预测，因燃煤电厂排放量增加，太平洋中汞含量将升高50%。

Consumers are now trying to understand how the USGS study’s findings should influence their eating habits. One popular national news programme displayed slices of raw fish on air and asked a health expert go through which ones were safe to consume. This shows the need for clearer guidance from the EPA and the Food and Drug Administration (FDA) on fish consumption by pregnant women, says Richard Wiles of the Environmental Working Group, which keeps an eye on toxins in food. He says the FDA has “historically been in the pocket of the tuna industry”, and has failed to give specific directives about how to get the health benefits of fish while avoiding mercury.
消费者开始理解美国地质调查局的研究结果会对饮食习惯产生怎样的影响了。有个大众性全国新闻栏目在节目中把生鱼片一字排开，让健康专家依次检查哪些可以放心食用。环境工作小组（Environmental Working Group）在密切关注食品中的有毒物质，其成员理查德•威尔斯说，这表明环保局和食品药品管理局（Food and Drug Administration，简称FDA）有必要为孕妇在食用鱼类方面给出更明确的指导。他说，食品药品管理局“历史上就一直管控着金枪鱼行业”，却没有告诉人们怎样健康吃鱼而避免汞中毒的具体指导。

The news about mercury also underscores the importance of developing a federal policy to control emissions. The Bush administration’s proposed cap-and-trade policy, which would have allowed heavily polluting factories to buy emission rights from cleaner ones, was struck down in court last year. That leaves Barack Obama responsible for suggesting a more aggressive curb on mercury emissions—for the good of America’s fish and those who eat them.
关于汞含量的新闻强调了制定联邦政策控制污染排放的重要性。布什政府提出一项封顶与贸易政策，允许重污染工厂从轻污染工厂购买排放权，该提议去年在法庭被驳回。这样一来，为了美国鱼类健康，为了美国食鱼者的健康，制定一项更积极遏制汞排放量政策的责任便落到了奥巴马身上。