Expert Meeting to review toxicological aspects of melamine a

专家会议审查三聚氰胺和氰尿酸的毒理学机理

Expert meeting to review toxicological aspects of melamine and

cyanuric acid

In collaboration with FAO

Supported by Health Canada

Ottawa Canada, 1 - 4 December 2008

OVERALL CONCLUSIONS AND RECOMMENDATIONS

OVERALL CONCLUSIONS AND RECOMMENDATIONS...................................................................................1 1 Chemistry of melamine and its analogues......................................................................................................1 2 Methods of analysis of melamine and its analogues in food and feed...........................................................2 3 Occurrence data.............................................................................................................................................2 4 Exposure assessment......................................................................................................................................4 5 Toxicological and epidemiological data........................................................................................................4 6 Derivation of the TDI.....................................................................................................................................6 7 Risk characterization......................................................................................................................................7 LIST OF PARTICIPANTS..........................................................................................................................................8

1 Chemistry of melamine and its analogues

Melamine is produced in large amounts (1.2 million tonnes in 2007) primarily for use in the synthesis of melamine formaldehyde resins for the manufacture of laminates, plastics, coatings, commercial filters, glues or adhesives, and dishware and kitchenware. Analogues (cyanuric acid, ammeline and ammelide) can be produced as impurities during the manufacturing process for melamine. They may also be produced by the bacterial metabolism of melamine if the melamine is not completely metabolized to ammonia and carbon dioxide.

Melamine can form self-associating, high molecular weight complexes through intramolecular networks of hydrogen bonds and π-π aromatic ring stacking interactions with cyanuric acid and other analogues as well as uric acid and other cyclic imide–containing biomolecules. The melamine added to adulterated milk for at least some of the infant formula produced in China that caused renal illnesses during the 2008 incident appeared to be relatively pure. Chinese infant formula reportedly contained levels of cyanuric acid, ammeline and ammelide that were only about 0.1% of the melamine levels and much lower than levels present in contaminated wheat gluten and rice protein concentrate ingredients that were used in the production of pet foods during the 2007 melamine contamination incident in the United States, Canada and South Africa.

专家会议审查三聚氰胺和氰尿酸的毒理学机理

Recommendations

Determine the melamine, uric acid and co-contaminant analogue (cyanuric acid, ammeline

and ammelide) residue profiles in renal stones from impacted Chinese infants, and determine the melamine and analogue content of the infant formula samples they consumed, as available.

Characterize the solubility properties, including thresholds for precipitation, of complexes

formed between melamine and the oxytriazine species detected in contaminated foods (cyanuric acid, ammelide and ammeline) and uric acid in vivo and in vitro.

2 Methods of analysis of melamine and its analogues in food and feed

Even though there are various methods currently in use for the screening, confirmation and quantification of melamine and its analogues, they have not been evaluated in an interlaboratory collaborative exercise. Thus, laboratories must thoroughly verify the performance of their method of choice for its intended purpose under their own laboratory conditions.

Liquid chromatography with tandem mass spectrometry and gas chromatography with tandem mass spectrometry are the techniques of choice for confirmatory analysis of melamine and its analogues because of their very high selectivity and high sensitivity.

Recommendations

Develop and thoroughly validate rapid, simple and low-cost screening methods that can

detect melamine plus its analogues in food and feed. Ideally, the new screening tools can be used outside of laboratory settings by various personnel.

Highly encourage all laboratories involved in melamine analysis to participate in organized

proficiency testing programmes for the analysis of melamine and its analogues in food and feed. FAO/WHO should investigate ways of encouraging and facilitating such programmes. Develop more specific, rapid and low-cost methods for protein analysis that do not include

non-protein nitrogen in order to monitor for, and ultimately prevent, adulteration with sources of non-protein nitrogen.

3 Occurrence data

For this report, the sources of melamine have been pided into “baseline” levels, which refer to levels in food that do not result from adulteration or misuse, and “adulteration” levels, which refer to levels in food that result from the intentional addition of melamine to food or unapproved use or misuse of melamine or substances that can degrade to form melamine.

Baseline concentrations of melamine are present in the environment and in the food-chain as a result of the widespread use of materials that contain melamine. Although data for baseline levels of melamine originating from certain sources, such as migration from tableware, were available, melamine occurrence data from ot …… 此处隐藏：23210字，全部文档内容请下载后查看。喜欢就下载吧 ……