Science Magazine - Chinese Probe Unmasks High-Tech Adulteration With Melamine

[Willow]

http://www.sciencemag.org/cgi/content/full/322/5906/1310

Chinese Probe Unmasks High-Tech Adulteration With Melamine

BEIJING--A weeks-long investigation into China's tainted milk scandal has left scientists astonished by the technical sophistication of those who used melamine to adulterate food products. Chinese investigators, meanwhile, are puzzling over the precise mechanisms of exposure and toxicity in infants who developed kidney damage.

At a closed workshop with U.S. experts here last week, Chinese scientists presented early results of an ongoing probe into the mass poisoning that left at least four infants dead and sickened more than 53,000 others after they drank baby formula tainted with melamine, an industrial chemical used primarily as a plastics stabilizer and fire retardant. The workshop capped a busy week in which the Chinese government trotted out measures to improve food safety, and the U.S. Food and Drug Administration (FDA) opened its first offices in China. "After melamine, there will be more transparency, more openness," says Chen Junshi, co-chair of the Sino-U.S. workshop and a risk-assessment specialist at China's Center for Disease Control and Prevention here. U.S. officials are speaking in more sweeping terms about the impact on $2 trillion worth of imports a year: "This is nothing short of a redesign of food and drug safety to meet a 21st century challenge," says U.S. Health and Human Services Secretary Michael Leavitt.

The melamine scandal came to light last September, when the central government learned that scores of infants in Gansu Province had been hospitalized with kidney stones, evidently after being fed infant formula with high levels of melamine. In the weeks that followed, powdered formula, fresh milk, and other products from some two dozen companies were found to contain melamine. Police have detained more than 30 people suspected of adulterating milk, including the general manager of one of China's largest powdered milk makers, Sanlu, based in Shijiazhuang. In an interview with Science last month, Premier Wen Jiabao expressed sorrow for the poisoning and vowed an aggressive response (Science, 17 October, p. 362).

Researchers say the adulteration was nothing short of a wholesale re-engineering of milk. Weeks ago, investigators established that workers at Sanlu and at a number of milk-collection depots were diluting milk with water; they added melamine to dupe a test for determining crude protein content. "Adulteration used to be simple. What they did was very high-tech," says Chen. Researchers have since learned that the emulsifier used to suspend melamine--a compound that resists going into solution--also boosted apparent milk-fat content.

Sanlu baby formula contained a whopping 2563 mg/kg of melamine, adding 1% of apparent crude protein content to the formula, says Jerry Brunetti, managing director of Agri-Dynamics in Easton, Pennsylvania. Milk, he notes, is only 3.0% to 3.4% protein. Chen says a dean of a school of food science told him that it would take a university team 3 months to develop this kind of concoction.

Investigators have concluded that as-yet-unidentified individuals cooked up a protocol for a premix, a solution designed to fortify foods with vitamins or other nutrients. In this case, it was deadly. Several milk-collecting companies were using the same premix, Chen says: "So someone with technical skill had to be training them."

So far, Chinese scientists have fingered only melamine as the toxic agent. Published studies on cats and rats indicate that melamine reacts with an accomplice--cyanuric acid--to form melamine cyanurate crystals found in kidney stones. Both melamine and cyanuric acid were present in wheat gluten imported from China during the North American pet-food recall last year; the mixture killed dozens of cats and sickened thousands of other pets.

In the tainted milk products, however, Chinese researchers have found only trace amounts of cyanuric acid--parts per billion, or roughly 1% of the amount of melamine in the samples, says Chen. "Our scientists concluded that melamine by itself caused the kidney stones. But one unresolved issue is how high the melamine levels have to be for this to happen." Some experts are skeptical. George Daston, a toxicologist with Procter & Gamble Co. in Cincinnati, Ohio, who with colleagues published a study in Toxicological Sciences online on 9 August, doubts that "melamine alone caused the kidney stones." He says that "melamine and cyanuric acid are so tightly associated with each other, it can be difficult to extract the compounds from the contaminated products." U.S. chemists "found melamine but not cyanuric acid in their initial attempts to identify the contaminant" in pet food, says Daston; subsequent analyses, he says, uncovered significant amounts of cyanuric acid. To settle questions about the new melamine cases, Chen says, "we need more data." The World Health Organization will hold an expert consultation on these issues in Ottawa next week.

Many other strands of the tragedy have yet to be unraveled. Although it's evident that adulteration was to blame for baby formulas with high melamine levels, it's unclear whether very low levels of melamine contamination--the lowest tested level was 0.09 ppm--might have come from nonprotein nitrogen (NPN) additives in ruminant feeds or from plastic packaging. NPN additives such as biuret and urea are used in cattle feed in many countries, including the United States. The Chinese government supported research in the 1990s on NPN feed additives and has encouraged their use. Since then, a cottage industry has sprung up selling dan bai jing (protein essence), whose specific ingredients are unknown, for use in livestock feeds.

China has heightened its vigilance, and the odds of melamine slipping through the safety net again are vanishingly low. But the problem of adulterated livestock feeds may be harder to resolve. After FDA traced last year's poisoned pet food to gluten from China tainted with melamine scrap--melamine, cyanuric acid, and related compounds--China's agriculture ministry issued a standard for determining levels of melamine in feeds and banned the use of this and other harmful compounds in June 2007. The ban appears to have had little effect. Authorities in Hong Kong recently uncovered melamine in eggs and in fish feed.

The measures announced last week should help keep attention focused on the contamination problem. The National People's Congress is expected to pass a new food-safety law next month that would establish a food-hazard monitoring system and a risk-assessment committee under the health ministry. Meanwhile, the governing State Council ordered the ministry last month to sort out confusing food standards. For instance, soy sauce, depending on how it's made and used, is subject to four standards. One unresolved problem is segmentation of food control and inspection, with one agency overseeing farms, another one responsible for food manufacturers, and so on up to the dinner table. "Scientifically, this is a terrible system," says Chen.

Last week, FDA opened three offices in China--in Beijing, Guangzhou, and Shanghai--whose eight inspectors and technical experts will team up with Chinese experts to monitor traffic in food products. It plans to open two offices in India next month and two in Latin America in January. China's State Food and Drug Administration also plans to open U.S. offices to share technical expertise and work more closely on policing imports. The global network "will require new science for detection and investigation of contamination," says FDA Commissioner Andrew von Eschenbach.

But the challenges facing China are immense. The country has 200 million farming households and more than 500,000 food manufacturers, many of which employ fewer than 10 people, says Chen. "Most companies don't care about their reputation," he says, and can dissolve and reconstitute elsewhere. "Food adulteration is inevitable and will be with us for many years."

Chen expects food and feed adulterators to raise their game. "The sophistication of the techniques will improve the next time," he says. Li Shaomin, a management professor at Old Dominion University in Norfolk, Virginia, who studies the business environment in China, agrees. "When millions of people experiment with new ways to make money without moral self-constraint, the chance of new products that can evade existing testing methods is pretty high," he says. "Unless the people who put melamine into milk lose sleep, the product-safety problem in China will go on."

[matrix]

乳制品三聚氰胺污染丑闻调查中透露出的高科技掺假令科学家震惊。婴儿奶粉三聚氰胺污染至少导致6名婴儿死亡，53000多名婴儿生病住院。调查结果 确认三鹿集团的员工和许多奶站用水稀释牛奶，添加三聚氰胺以欺骗粗蛋白质含量测试。疾病预防控制中心风险评估专家陈君石表示，"掺假通常很简单，但他们所 做的却是十分的高科技。"他认为肯定有人在教他们。三鹿婴儿配方奶粉包含惊人的2563 mg/kg三聚氰胺，表面上在配方中加入1%的粗蛋白质含量，实际上相当于3.0%到3.4%蛋白质(注：这句话可能有点问题)。陈称一位食品科学系的系主任告诉他，一个大学团队需 要三个月才能开发出这类的混合比例。《科学》杂志的文章表示， 悲剧中还有更多未解之谜没有揭开，高浓度的三聚氰胺显然是故意掺杂的，但目前并不清楚低含量的三聚氰胺——最低为0.09 ppm——是来自饲料中的非蛋白氮（NPN）添加剂还是来自塑料包装。NPN添加剂如缩二脲和尿素在许多国家被广泛使用于动物饲料中，其中包括美国。中国政府在1990年代开始支持NPN添加剂研究，并鼓励使用。自那时起，出售蛋白精的家庭作坊迅速成长起来。 "

2008/11/29 Willow <chengy...@gmail.com>

--
http://www.solidot.org