Survey of counterfeit melamine tableware available on the market in Thailand, and its migration

Migration of Melamine and Its Derivatives from Melamine/Bamboo/Wheat Straw-Made Tableware Purchased from Internet Markets or Retail Shops in China

OBJECTIVES

The ecofriendly and sustainable concept of bamboo- and wheat straw-made tableware has gained attention in recent years. However, it is necessary to note that these kinds of tableware are composed of melamine (MEL)-formaldehyde resin with the addition of bamboo fibers or wheat straw. This study aims to explore the potential migration of MEL and its derivatives from the tableware and conduct a risk assessment.

METHODS

The study involved 46 bowls or cups purchased from Internet markets or retail shops in China, whose raw materials included MEL, bamboo, and wheat straw. There were four pieces of glass- or ceramic-made tableware used as the control group. Migration testing was performed according to the test conditions selected from the European Union Reference Laboratory for Food Contact Materials. Considering the realistic worst-case scenario, we measured the concentrations of MEL and its derivatives in food simulants using ultra-performance liquid chromatography-tandem mass spectrometry and estimated the exposure risks for adults and 1-year-old infants.

RESULTS

MEL and its derivatives could migrate from MEL-, bamboo-, and wheat straw-made tableware with varying concentrations. The total migration was ranked as follows: bamboo-made tableware > MEL-made tableware > wheat straw-made tableware > glass- or ceramic-made tableware (p < 0.001). The primary contributor to the total concentration for MEL- and bamboo-made tableware was MEL, whereas cyanuric acid (CYA) was the main contributor for wheat straw-made tableware. Based on the total concentration of MEL and its derivatives and the strictest TDI value, the proportions of the calculated hazard quotient ≥1 for MEL-, bamboo-, and wheat straw-made tableware in adults were 53.50%, 92.30%, and 1.90%; and the proportions in 1-year-old infants increased to 86.00%, 100.00%, and 7.40%.

CONCLUSION

The utilization of MEL-, bamboo-, and wheat straw-made tableware could be regarded as a significant source of human exposure to MEL and its derivatives. It is advisable for both adults and infants to refrain from using tableware manufactured with MEL and bamboo fiber, as it may increase the susceptibility to MEL-related diseases.

Twenty-four-hour temporal trend of melamine and its derivatives in urine in association with meal consumption: a panel study in Shanghai, China

Timing of sampling is important for the exposure assessment of melamine (MEL) and its derivatives. This study aimed to investigate whether MEL and its derivatives in spot urine can effectively represent individual exposure levels throughout the day in adults and to explore their temporal trend before and after meal consumption for helping understand the timing of sampling and for assessing the potential exposure risk. This is a 2-day panel study with 43 college students being enrolled to provide urine specimens in 24 h (from the morning of the first day to the second day) and to answer a questionnaire on demographic characteristics, physical measurements, and time of having meal. Spearman correlation and Wilcoxon rank-sum test were used to examine the associations of the urinary concentrations of MEL and its derivatives in different sampled times and compare the concentrations' differences before and after meal consumption. Urinary concentrations of MEL and its derivatives (ammeline (AMN), ammelide (AMD), and cyanuric acid (CYA)) in the first-morning urine at the second day and randomly selected spot urine were positively associated with the average concentrations in the previous 24-h urine (all P ≤ 0.002). Urinary MEL concentration increased rapidly after meal consumption, reaching a maximum at approximately 3 h and then decreased gradually towards baseline (P = 0.006). Two subjects (4.65%) had a cumulative daily intake exceeding the severest tolerable daily intake. MEL and its three derivatives in spot urine can effectively represent the average concentrations in the previous 24-h urine in adults. Meal consumption is still a notable source of exposure to MEL for humans. These findings are important for choosing a better sampling strategy of performing exposure assessment. Meanwhile, the acute elevation in urinary MEL concentration following meal consumption may pose a potential health risk.

Migration of formaldehyde and melamine from melaware and other amino resin tableware in real life service

The migration of formaldehyde and melamine monomers has been measured on 90 samples of plastic tableware in three different situations - new articles, already used articles and artificially aged articles - by using simulant, contact times and temperatures prescribed by Commission Regulation (EU) No. 10/2011. Formaldehyde was determined by ultraviolet spectroscopy analysis of the coloured complex obtained by reaction with chromotropic acid. Melamine was measured by an ultra high performance liquid chromatography method. Fourier Transformed - Infrared Analysis was applied to characterise the plastic. The results highlighted the presence of different amino resins based on formaldehyde-melamine, urea-formaldehyde or melamine-urea-formaldehyde with different migration behaviour. The migration of monomers was related to progressive degradation of the resins. Ageing studies demonstrated that the potential degradation of the resins and the consequent migration of the monomers may continue throughout the service life of the product. The specific migration limit (SML) of melamine was exceeded after ageing.