Chromatographic analysis of dithiocarbamate residues and their metabolites in foods employed in dietary exposure studies-a review.

Dithiocarbamates (DTCs) belong to a group of compounds used as fungicides in food production and can be divided into three major groups. Since DTCs easily oxidise and hydrolyse in alkaline and acidic medium respectively, precautions have to be implemented during preparation/homogenisation and extraction of samples. As such, test samples are commonly prepared individually by cutting into small pieces just before the digestion of DTCs with a hot acid to give carbon disulphide (CS2) and the results are expressed as CS2 without any differentiation of individual DTCs. However, individual DTCs have different toxicological potencies whilst their metabolites are more toxic than the parent compound. Apart from the hot digestion method, chromatographic separation of three major groups of DTCs has been developed by a number of different researchers. This review provides a comprehensive examination of sample preparation, extraction, clean-up and chromatographic methods for the determination of individual DTCs and their more toxic metabolites in foodstuffs. Moreover, this review also studies on how dietary exposure of DTCs can be efficiently and effectively estimated using different methods of analysis.

Dietary exposure of Hong Kong adults to pesticide residues: results of the first Hong Kong Total Diet Study.

The use of pesticides and other chemicals has become a common practice in modern agriculture to enhance and stabilise crop yield, protect the nutritional integrity of food, facilitate food storage to assure year-round supplies, and provide attractive and appealing food products. With the adoption of strict good agricultural practice (GAP), only minimal amounts of pesticide residues should remain on the crops or in connected foods of animal origin up the food chain. To assess their associated health risk to local people, the dietary exposure of Hong Kong adults to residues of four groups of pesticides or their metabolites - organophosphorus pesticides (OPPs), carbamates, pyrethrins and pyrethroids, and dithiocarbamate (DTC) metabolites - is estimated in the first Hong Kong Total Diet Study (TDS). A total of 150 commonly consumed food items were collected and prepared "as consumed". A total of 600 composite food samples were analysed for 85 pesticides or their metabolites by liquid chromatography-tandem mass spectrometry (LC-MS/MS). These pesticides were primarily found at low levels (highest mean = 350 µg kg⁻¹) in food samples of plant origin such as vegetables and fruits. Dietary exposures to pesticide residues were estimated based on the analytical results and the food consumption data of the local residents. The estimated dietary exposures of Hong Kong adults to all individual pesticides were well below their respective acceptable daily intakes (ADIs). The percentage contributions of the estimated mean and 95th percentile dietary exposures to the ADIs of individual pesticides were <6% and <24% for the OPPs, <1% for the carbamates and pyrethrins and pyrethroids, and <1% and <4% for the DTC metabolites, respectively. The findings indicate that dietary exposures to all the pesticide residues analysed in this study were unlikely to pose unacceptable health risks to the Hong Kong population.

Dietary exposure of Hong Kong adults to acrylamide: results of the first Hong Kong Total Diet Study.

Acrylamide is a processing contaminant in food formed during cooking at high temperature, such as frying and baking. To assess the associated health risk of the Hong Kong population, the dietary exposure of Hong Kong adults to acrylamide was estimated in the first Hong Kong Total Diet Study (TDS), where food samples were collected and prepared "as consumed". A total of 532 composite food samples were analysed for acrylamide using LC-MS/MS. Dietary exposures were estimated by combining the analytical results with the food consumption data of the Hong Kong adults. The mean and 95th percentile exposures to acrylamide of the Hong Kong population were 0.213 and 0.538 µg kg⁻¹ body weight (bw) day⁻¹, respectively, and their margins of exposure (MOEs) were all below 10,000. The main dietary source of acrylamide was "Vegetables and their products" (52.4% of the total exposure), particularly stir-fried vegetables (44.9%), followed by "Cereals and their products" (14.7%) and "Mixed dishes" (9.43%). The study findings suggest that the relatively low figures for MOE for a genotoxic carcinogen may indicate human health concern of the Hong Kong population. Efforts should continue to be made in the interest of reducing acrylamide levels in food locally.

Dietary exposure to dioxins and dioxin-like PCBs of Hong Kong adults: results of the first Hong Kong Total Diet Study.

Dioxins and dioxin-like polychlorinated biphenyls (PCBs) are persistent organic pollutants (POPs) covered by the Stockholm Convention on POPs. To assess the associated health risk of the Hong Kong population, the dietary exposure of the Hong Kong population and various age-gender subgroups to dioxins and dioxin-like PCBs was estimated in the first Hong Kong Total Diet Study (TDS), where food samples were collected and prepared "as consumed". A total of 142 composite food samples, mainly foods of animal origin and their products and oily food, were analysed for polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) and dioxin-like PCBs by the high-resolution gas chromatograph/high-resolution mass spectrometer (HRGC/HRMS) system. Dietary exposures were estimated by combining the analytical results with the food consumption data of Hong Kong adults. The mean and 95th percentile exposures to dioxins and dioxin-like PCBs of the Hong Kong population were 21.9 and 59.7 pg toxic equivalent (TEQ) kg⁻¹ body weight (bw) month⁻¹ respectively, which amounted to 31.3% and 85.2% of the provisional tolerable monthly intake (PTMI). The main dietary source of dioxins and dioxin-like PCBs was "Fish and seafood and their products" (61.9% of the total exposure), followed by "Meat, poultry and game and their products" (20.0%) and "Mixed dishes" (6.95%). The study findings suggest that the Hong Kong population is unlikely to experience the major undesirable health effects of dioxins and dioxin-like PCBs.

Dietary exposure to inorganic arsenic of the Hong Kong population: results of the first Hong Kong total diet study.

Inorganic arsenic, a human carcinogen, can be found in the environment and food. In the first Hong Kong Total Diet Study, the dietary exposure of the Hong Kong people, including various age-gender subgroups, to inorganic arsenic was estimated for assessing the associated health risk. Food samples, which represented the Hong Kong people's diet, were collected and prepared "as consumed" for analysis. Concentrations of inorganic arsenic, as sum of arsenite (As(III)) and arsenate (As(V)) were determined in 600 composite samples by using inductively coupled plasma mass spectrometry. The dietary exposures were estimated by combining the analytical results with the local food consumption data of the adult population. The mean and 95th percentile of inorganic arsenic exposures of the Hong Kong people were 0.22 and 0.38µg/kg body weight (bw)/day, respectively. Among the 12 age-gender subgroups, the respective exposures ranged from 0.19 to 0.26µg/kg bw/day and from 0.33 to 0.46µg/kg bw/day. The main food category that contributed inorganic arsenic was "cereals and their products" (53.5% of the total exposure), particularly rice. Having considered the carcinogenic risk of inorganic arsenic to humans, it is suggested that efforts should be made to reduce the inorganic arsenic exposure of the Hong Kong population.

Dietary exposure to aluminium of the Hong Kong population.

A total of 256 individual food samples were collected in Hong Kong for aluminium testing. Most of food samples were analysed in ready-to-eat form. High aluminium levels were found in steamed bread/bun/cake (mean: 100-320 mg kg(-1)), some bakery products such as muffin, pancake/waffle, coconut tart and cake (mean: 250, 160, 120 and 91 mg kg(-1), respectively), and jellyfish (ready-to-eat form) (mean: 1200 mg kg(-1)). The results demonstrated that aluminium-containing food additives have been widely used in these food products. The average dietary exposure to aluminium for a 60 kg adult was estimated to be 0.60 mg kg(-1) bw week(-1), which amounted to 60% of the new PTWI established by JECFA. The main dietary source was "steamed bread/bun/cake", which contributed to 60% of the total exposure, followed by "bakery products" and "jellyfish", which contributed to 23 and 10% of the total exposure, respectively. However, the estimation did not include the intake of aluminium from natural food sources, food contact materials or other sources (e.g. drinking water). Although the results indicated that aluminium it is unlikely to cause adverse health effect for the general population, the risk to some populations who regularly consume foods with aluminium-containing food additives cannot be ruled out.

Dietary exposure to antimony, lead and mercury of secondary school students in Hong Kong.

The aim of this first study was to determine the dietary exposure of antimony, lead, mercury in foodstuffs consumed by secondary school students in Hong Kong. Around 100 composite food items were purchased and then cooked prior to analysis. Antimony was measured by hydrogen generation (HG)/inductively coupled plasma-mass spectrometry (ICP-MS), while lead was determined by ICP-MS. Total mercury was measured by cold vapour atomic absorption spectrometry. The detection limits for antimony, lead and total mercury were 1, 0.6 and 3 microg kg(-1), respectively. The dietary intake of antimony, lead and total mercury for an average secondary student were estimated to be 0.252, 1.98 and 0.92 microg (kg bw)(-1) week(-1), respectively. The dietary intake of antimony, lead and total mercury for high-consumer secondary student were estimated to be 0.567, 5.09 and 2.33 microg (kg bw)(-1) week(-1), respectively. The main contribution to antimony, lead and mercury were milk, vegetables and seafood, respectively. The Tolerable Daily Intake (TDI) of antimony, as recommended by WHO, is 6 microg (kg bw)(-1) week(-1), while the Provisional Tolerable Weekly Intakes (PTWI) of lead and mercury, as recommended by JECFA, are 25 and 5 microg (kg bw)(-1) week(-1), respectively. The estimated exposure values for secondary school students were compared to these safety reference values. For the relevant population, this study confirms the low probability of health risks from these metals via food consumption.