Risk Assessment Studies
Report No. 29
Chemical Hazard Evaluation
DIETARY EXPOSURE TO CHLOROPROPANOLS OF
SECONDARY SCHOOL STUDENTS
Centre for Food Safety
Food and Environmental Hygiene Department
The Government of the Hong Kong Special Administrative Region
Risk Assessment Section
Centre for Food Safety,
Food and Environmental Hygiene Department,
43/F, Queensway Government Offices,
66 Queensway, Hong Kong.
Table of Contents
|Limitations of the Exposure Assessment Study|
|Conclusion and Recommendation|
|Annex: Levels of Chloropropanols in Foods|
Risk Assessment Studies
Report No. 29
DIETARY EXPOSURE TO CHLOROPROPANOLS OF
SECONDARY SCHOOL STUDENTS
This study examined the levels of two types of chloropropanols, namely 3-monochloropropan-1,2-diol (3-MCPD) and 1,3-dichloro-2-propanol (1,3-DCP), in a wide range of food items, estimated the dietary exposure to the above two chloropropanols of secondary school students in Hong Kong and assessed the associated health risks based on the available data.
Dietary exposure to chloropropanols was estimated using the local food consumption data obtained from secondary school students in 2000 and the concentrations of 3-MCPD and 1,3-DCP in food samples taken from the local market. Laboratory analysis for 3-MCPD and 1,3-DCP was conducted by the Food Research Laboratory of the Centre for Food Safety.
The dietary exposure to 3-MCPD for an average consumer of secondary school student was estimated to be 0.063 – 0.150 m g/kg bw/day whilst that for the high consumer was 0.152 – 0.300 m g/kg bw/day . Both estimates fell below the provisional maximum tolerable daily intake of 2 m g/kg bw established by JECFA and amounted to less than 20% of this safety reference value. The dietary exposure to 1,3-DCP for an average consumer of secondary school student was estimated to be 0.003 – 0.019 m g/kg bw/day whilst that for the high consumer was 0.009 – 0.040 m g/kg bw/day. The resulting margin of exposures were of low concern for human health.
It could be concluded that both the average and high consumers of the secondary school students were unlikely to experience major toxicological effects of 3-MCPD and 1,3-DCP.
The results also showed that the food group "cereal and their products", particularly instant noodle, was the main dietary source of 3-MCPD. This might due to the fact that the soup base for instant noodle might contain acid-HVP as a savoury ingredient. As the dietary exposure to 3-MCPD upon consumption of instant noodle soup had not been taken into account in this study, the exposure estimates were expected to be higher for those consumers of the instant noodle soup. On the other hand, "meat, poultry and their products", particularly sausage, was the main dietary source of 1,3-DCP.
The trade is advised to reduce the levels of chloropropanols in food as far as is technically achievable. Members of the public are advised to maintain a balanced diet so as to avoid excessive exposure to contaminants from a small range of food items.
Dietary Exposure to Chloropropanols of
Secondary School Students
This study aims to examine the levels of two types of chloropropanols, namely 3-monochloropropan-1,2-diol (3-MCPD) and 1,3-dichloro-2-propanol (1,3-DCP), in a wide range of food items and to estimate the potential dietary exposure to these chloropropanols of secondary school students in Hong Kong . The associated health risks will be assessed based on the estimations.
2. In recent years there has been increasing interest in chloropropanols (also known as chlorinated propanols) globally. These chemicals have received attention in HKSAR since 1999 when a survey of soya sauce conducted in the United Kingdom by the former Ministry of Agriculture Fisheries and Food (MAFF) revealed that some local brands contained 3-MCPD.1
3. Certain chloropropanols, including 3-MCPD and 1,3-DCP, were originally identified as contaminants of the savoury ingredient, acid-hydrolysed vegetable protein (acid-HVP), which is formed by treating defatted vegetable proteins with hydrochloric acid. Because of the wide application of acid-HVP, 3-MCPD and 1,3-DCP have been identified in many other foods, particularly sauces and condiments such as soya sauce and oyster sauce. 3-MCPD and 1,3-DCP can also form in food as a result of heat processing ( e.g., baking of cereal products), as well as other processing or storage conditions, but the exact mechanisms for their formation have not been fully understood.2,3,4
4. To address the food safety concern of chloropropanols, food safety authorities have conducted toxicological evaluation and dietary surveys of chloropropanols in food. The Joint Food and Agriculture Organization (FAO) / World Health Organization (WHO) Expert Committee on Food Additives (JECFA) evaluated the safety of 3-MCPD and 1,3-DCP in 2001 and re-evaluated the two contaminants in 2006. The Codex Alimentarius Commission (Codex) has been discussing the issue and proposing relevant standard and code of practice since 2000. On the other hand, food authorities from places such as the member countries of the European Commission5 and Australia6 have been collecting data on levels of chloropropanols in different food items and conducting estimates on dietary exposure.
5. In response, FEHD has included the testing of 3-MCPD in its routine food surveillance programme and adopted an action level of 1 mg/kg since 1999. Special studies on 3-MCPD in soya sauce as well as oyster sauce and related products were conducted jointly with the Consumer Council in 2002 and 2004 respectively. The results showed that the levels of 3-MCPD in all samples fell below the action level.7, 8Lacking local data on the levels of chloropropanols in other food items, dietary exposure estimates could not be determined and the associated health risks to the local population are not clear. A study on chloropropanols in food is therefore needed to examine the situation in the local scene.
6. 3-MCPD is also known as chlorohydrin, glycerol chlorohydrin, 3-chloropropan-1,2-diol and 1-chloropropane-2,3-dihydroxypropane. 4 It is present in a wide range of food items due to routes and mechanisms discussed below:
7. The most well-known route of formation of 3-MCPD is the hydrolysis of vegetable protein using concentrated hydrochloric acid. The raw materials are usually derived from soya flour, soya meal, wheat, corn, rapeseed meal and potato. Hydrochloric acid as well as triacylglycerols, phospholipids and glycerol in the raw materials have been demonstrated to be the precursors of chloropropanols. 4
8. Liquid seasoning condiments such as soya sauce, oyster sauce, fish sauce, etc., which have been produced using an acid treatment or included acid-HVP as an ingredient, have been found to contain 3-MCPD. Other food products that may contain acid-HVP, for example, instant noodle, garlic powder, spice mixture, mixes for soups, broths, sauces and gravies, snacks such as potato chips, as well as composite foods such as hamburgers, have also been reported to contain 3-MCPD.4
9. 3-MCPD has been found to occur in a wide range of other food items without the presence of the ingredient acid-HVP. It appears that the presence of lipids and sodium chloride contribute to the formation of 3-MCPD during normal heat processing steps such as baking, grilling and roasting. The most studied model is bread-making. Factors affecting the formation of 3-MCPD in bread include moisture content, temperature, pH as well as the types of esters of fatty acids and food additives present in the food. The presence of glycerol at low moisture content, lecithin at high moisture content, mono- or di-esters of fatty acids of 3-MCPD, temperatures above 170oC, flour improver such as diacetyltartaric acid and fatty acid esters of glycerol have been shown to promote the 3-MCPD formation. On the other hand, relatively high pH (above pH 6.0) and the presence of sodium bicarbonate have been found to inhibit its formation. In contrast, the levels of acrylamide in these bakery products were found to increase with increasing pH value.4
Fatty acid esters of 3-MCPD
10. Recent studies found that fatty acid esters of 3-MCPD, i.e., bound 3-MCPD, were found in various foodstuffs such as pickled olives, roasted and green coffee, crisp bread, soda crackers, potato crisps and French fries, salami, certain types of ham, smoked and pickled fish, as well as some cheeses. 3-MCPD has been shown to release under certain processing conditions, such as enzymatic hydrolysis by bakery grade lipase during the baking process. 4
11. The presence of 3-MCPD in some of food may be contributed by its migration from certain types of epichlorohydrin-based wet strength resins used in paper and cellulose casings, e.g., sausage casings, tea bags and coffee filter paper.4
12. A number of smoked foods was also found containing 3-MCPD. However, the parameters that affect 3-MCPD generation in these products are still being studied. The exact mechanism for the formation of 3-MCPD in different foods in fact has not been fully understood yet. Salami, though reported to have 3-MCPD up to 29 mg/kg, was found not containing acid-HVP as a food ingredient and not demonstrating to have the evidence of lipid hydrolysis to release 3-MCPD from its esters during storage.4
Other types of chloropropanols
13. Another type of well-known chloropropanol is 1,3-DCP. It has been reported that the levels of 1,3-DCP in acid-HVP food ingredients, soya sauce and related products are generally lower than those of 3-MCPD. In addition to sauces, 3-MCPD and 1,3-DCP have been found in cooked minced beef, ham and sausage. However, 1,3-DCP alone has also been detected in raw minced beef, ham and sausage meat. It has been suggested that more than one route is involved in the formation of 1,3-DCP and the exact mechanism is still under exploration.4,6
14. JECFA 2,3 has evaluated the safety of the two types of chloropropanols of most concern, i.e., 3-MCPD and 1,3-DCP. The toxicological significance of other types of chloropropanols, including the fatty acid esters of 3-MCPD, has not been determined yet. The safety of 3-MCPD and 1,3-DCP is briefly summarised below.
Kinetics and metabolism
15. 3-MCPD has been shown to be widely distributed in body fluid and cross blood-brain barrier and blood-testis barrier. Upon intraperitoneal administration of 3-MCPD, about 30% was shown to exhale as carbon dioxide whereas 8.5% was excreted unchanged in the urine. 3-MCPD was also found to be detoxified by conjugation with glutathione and oxalic acid would be formed subsequently. On the other hand, being a haloalcohol, there is ample evidence that it may undergo microbial enzymatic reaction to form glycidol, which has been shown to be genotoxic in vitro and in vivo.2
16. The reported oral median lethal dose (LD50 ) value in rats was 150 mg/kg body weight (bw).2
Genotoxicity and carcinogenicity
17. 3-MCPD was shown to be genotoxic in most in vitro assays but non-genotoxic in in vivo ones. JECFA raised questions about the relevancy of these in vitro tests because very high concentrations were used. JECFA concluded that 3-MCPD is not genotoxic in vitro at concentrations that are not toxic and in vivo. 2
18. Although 3-MCPD was found to be associated with increased incidences of benign tumours in some organs in an animal study, such tumours were observed only at dose levels greater than those causing other toxic effects. 2
Other chronic effects
19. 3-MCPD was shown to affect the kidney, the central nervous system and the male reproductive system of rats. A decrease in the motility of human spermatozoa by 3-MCPD synergistically with copper ions has also been demonstrated in vitro. 2
Safety reference value
20. JECFA established a provisional maximum tolerable daily intake (PMTDI) of 2 m g/kg bw/day for 3-MCPD on the basis of the lowest-observed-effect-level (LOEL) of 1.1 mg/kg bw/day for tubule hyperplasia observed in the kidney of rats and a safety factor of 500 (100 for inter- and intra-species variation and an extra factor of 5 for extrapolation from a LOEL to a no-observed-effect-level (NOEL)). 2 JECFA retained this PMTDI in its re-evaluation in 2006.9
Kinetics and metabolism
21. The studies on kinetics and metabolism for 1,3-DCP were limited. Animal studies found that about 5% or less of an oral dose of 1,3-DCP was excreted in the urine. 1,3-DCP was also found to be conjugated with glutathione and oxalic acid would be formed subsequently. 3
22. The reported oral LD 50 values in rats ranged from 120 to 140 mg/kg bw. 3
Genotoxicity and carcinogenicity
23. JECFA in 2001 considered that 1,3-DCP was clearly mutagenic and genotoxic in various bacterial and mammalian test systems in vitro and there was no data on intact mammalian organisms or humans. Regarding its carcinogenicity, an animal study demonstrated that 1,3-DCP increased the incidences of both benign and malignant neoplasms in at least three independent tissues in rats. 3
Other chronic effects
24. 1,3-DCP was found to affect the kidney and the liver of rats. It has also been reported to be hepatotoxic in humans upon occupational exposure. 3
Safety reference value
25. JECFA in 2001 concluded that it would be inappropriate to estimate a tolerable intake for 1,3-DCP because of the nature of the toxicity. 3 In 2006, JECFA concluded that carcinogenicity is the critical effect of 1,3-DCP and its genotoxicity cannot be excluded. After the analysis of the cancer dose-response data by dose-response modelling, a benchmark dose lower confidence limit a of a 10% incidence (BMDL10) value of 3.3 mg/kg bw/day was identified. JECFA has made use of this BMDL10 value for calculating the margin of exposure b (MOE) for the evaluation of risks for the estimated intakes of 1,3-DCP in its evaluation in 2006. 9
Dietary exposure estimates from foods other than sauces
Scope of study
26. To estimate the dietary exposures to 3-MCPD and 1,3-DCP from foods other than sauces, eight major food groups, namely (i) cereals and their products, (ii) vegetables and their products, (iii) fruits, (iv) fish, shellfish and their products, (v) meat, poultry, and their products, (vi) egg and their products, (vii) dairy products, as well as (viii) snacks, were covered. The selection was based on the reported occurrence of 3-MCPD and 1,3-DCP in these food groups and the consumption patterns.
Food consumption data
27. The food consumption data in this study was extracted from the Food Consumption Survey conducted in local secondary school students in 2000 by the FEHD. In the survey, a stratified three-stage sampling plan was used, with a sampling frame of 472 secondary schools and more than 380,000 students, covering almost all the local secondary schools. A total of 967 students from 27 schools participated in the survey yielding a response rate of 77% at the school level and 96% at the student level. The mean body weight of the participated students was 52.0 kg.10
28. Food samples were taken from the local market according to the above eight food groups. Food items were selected based on the results of the Food Consumption Survey and the likely occurrence of 3-MCPD and 1,3-DCP. Three samples of each food item were taken randomly from different sources for laboratory analysis.
29. Sample preparation and laboratory analysis were conducted by the Food Research Laboratory of the Centre for Food Safety. Food samples were treated and analysed as consumed so as to give a better estimate of the levels of 3-MCPD and 1,3-DCP that might be consumed. In view of lacking consumption data on instant noodle soup, the instant noodle samples were cooked according to the instruction on the food label and the soup was discarded before further sample preparation. As 3-MCPD may be formed during heat processing, selected beef, pork, chicken and fish samples were steamed and shallow-fried respectively to simulate the possible levels of 3-MCPD formed under low temperature (i.e. boiling, steaming, stewing, etc.) and high temperature (i.e. frying, grilling, braising, etc.) cooking processes. During the estimation of dietary exposures, the levels of chloropropanols for that particular food item were approximated in the proportions of the popularity of different cooking methods being employed in the preparation of that particular food item, based on the data collected in the Food Consumption Survey.10
30. 3-MCPD and 1,3-DCP in prepared food samples were extracted with concentrated sodium chloride solution, followed by separation and purification by liquid-liquid extraction. A portion of concentrated sample extract was subject to derivatization with heptafluorobutyrylimidazole (HFBI) and then analysis by gas chromatography / mass spectrometry (GC/MS). The limits of detection (LODs) for 3-MCPD and 1,3-DCP were 2.5 μ g/kg (ppb) and 0.5 μ g/kg (ppb) respectively. The adopted LODs are comparable to those used by authorities in the international arena for dietary exposure assessment and are in fact lower than the ones adopted in Australia.6
31. When the analytical value was below the LOD, the true value of 3-MCPD or 1,3-DCP in the food sample could be anywhere between zero and the LOD. The treatment for these results was particularly important when a large percentage of the analytical results of a particular food group fell below the LOD. While it may not be appropriate to assume a zero concentration for all samples with analytical values below LOD, assigning these non-detects a value of LOD, would, however, grossly overestimate the dietary exposure. In this study, recommendation from WHO regarding evaluation of low-level of contamination of food was followed when treating analytical value below LOD.11
Estimation of dietary exposure
32. Daily dietary exposures to 3-MCPD and 1,3-DCP from an individual food item were obtained by combining the consumption data and the levels of 3-MCPD and 1,3-DCP of that food item. Total exposure for each secondary school student was obtained by summing exposures from all food items. The mean and the 95th percentile of the daily exposure levels were used to represent the dietary exposure for average and high consumers respectively.
33. The estimated exposure level of 3-MCPD was then compared with the PMTDI established by JECFA, whereas that of 1,3-DCP was combined with the BMDL10 value recommended by JECFA for calculating the respective MOEs.
Results of exposure assessment
Food consumption data
34. Food consumption data for the nine food groups are given in Table 1.
Table 1: Food Consumption Pattern for Secondary School Students
|Food groups||Mean consumption
|Cereal and their products||493.2|
|Vegetables and their products||313.6|
|Fish, shellfish and their products||121.7|
|Meat, poultry and their products||187.0|
|Egg and their products||14.1|
Concentrations of chloropropanols in food
35. A total of 318 individual food samples were tested for 3-MCPD and 1,3-DCP. The test results for each food group are summarised in Table 2 whereas those for individual food samples are presented in Annex.
Table 2: Concentrations of 3-MCPD and 1,3-DCP in Foods
|Food groups||No. of samples||
|No. of detects||% of detects||Concentration range ( m< g/kg)||No. of detects||% of detects||Concentration range ( m g/kg)|
|Cereal and their products||57||31||54||< LOD – 23||0||0||–|
|Vegetables and their products||39||0||0||–||0||0||–|
|Fish, shellfish and their products||66||15||23||< LOD – 33||9||14||< LOD – 6.0|
|Meat, poultry and their products||87||46||53||< LOD – 32||6||7||< LOD – 9.5|
|Egg and their products||12||0||0||–||0||0||–|
|Snack||24||9||38||< LOD – 66||0||0||–|
LODs for 3-MCPD and 1,3-DCP were 2.5 μ g/kg (ppb) and 0.5 μ g/kg (ppb) respectively.
36. 3-MCPD was detected in food groups "cereal and their products", "fish, shellfish and their products", "meat, poultry and their products" and "snack", but not in food groups "vegetable and their products", "fruits", "egg and their products" and "dairy products". On the other hand, 1,3-DCP was only detected in low levels in "meat, poultry and their products" and "fish, shellfish and their products", but not in other food groups. Association between the formation of 3-MCPD and 1,3-DCP was not observed.
37. According to the WHO's recommendation on evaluation of low-level of contamination of food, 1 1 two estimates using 0 and LOD for all the results less than LOD are produced when greater than 60% but smaller and equal to 80% of results are below LOD and with at least 25 results quantified. The same recommendation is also applied to the condition when greater than 80% of test results fall below LOD. In our study, 68% of test results for 3-MCPD were below LOD and 85% of test results for 1,3-DCP were below LOD. The concentrations of 3-MCPD and 1,3-DCP for each food group and hence the dietary exposure estimates for these two contaminants were therefore presented in range. The upper bound was calculated by setting analytical values below LOD to LOD while the lower bound was calculated by setting analytical value below LOD to zero.
Dietary exposure to 3-MCPD
38. The dietary exposure to 3-MCPD for the average consumer of secondary school student was estimated to be 0.058 – 0.139 m g/kg bw/day . The main dietary source of 3-MCPD was "cereal and cereal products" which contributed to 40-56% of the total exposure. Dietary exposure to 3-MCPD from different food groups are shown in Table 3.
Table 3: Dietary Exposure to 3-MCPD for Average Consumer of Secondary School Student ( m g/kg bw/day) (% contribution)
|Food groups||Lower bound||Upper bound|
|Cereal and their products||0.032 (56%)||0.055 (40%)|
|Vegetables||0.000 (0%)||0.019 (14%)|
|Fruits||0.000 (0%)||0.019 (13%)|
|Fish, shellfish and their products||0.002 (4%)||0.009 (6%)|
|Meat, poultry and their products||0.021 (36%)||0.024 (17%)|
|Egg and their products||0.000 (0%)||0.001 (1%)|
|Dairy products||0.000 (0%)||0.009 (6%)|
|Snack||0.002 (4%)||0.003 (2%)|
39. Further analysis was undertaken to estimate the risk that high consumers might be exposed to. The 95th percentile exposure level of the secondary school students was used to represent the dietary exposure to 3-MCPD for a high consumer and was estimated to be 0.147 – 0.289 m g/kg bw/day (Table 4).
Table 4: Comparison between PMTDI Established by JECFA and Dietary Exposures to 3-MCPD from Foods Other Than Sauces for Average and High Consumers of Secondary School Students ( m g/kg bw/day) (% of PMTDI)
( m g/kg bw/day)
|Average consumer||High consumer|
|2||0.058 (3%) to 0.139 (7%)||0.147 (7%) to 0.289 (14%)|
Dietary exposure to 1,3-DCP
40. Dietary exposure to 1,3-DCP for the average consumer of secondary school student was estimated to be 0.003 – 0.019 m g/kg bw/day . The main dietary source of 1,3-DCP at the lower bound was "meat, poultry and their products" and that at the upper bound was "cereal and their products". Dietary exposure to 1,3-DCP from different food groups are shown in Table 5.
Table 5: Dietary Exposure to 1,3-DCP for Average Consumer of Secondary School Student m g/kg bw/day (% contribution)
|Food groups||Lower bound||Upper bound|
|Cereal and their products||0.000 (0%)||0.005 (26%)|
|Vegetables and their products||0.000 (0%)||0.003 (17%)|
|Fruits||0.000 (0%)||0.003 (16%)|
|Fish, shellfish and their products||0.001 (24%)||0.002 (10%)|
|Meat, poultry and their products||0.002 (76%)||0.004 (21%)|
|Egg and their products||0.000 (0%)||0.000 (1%)|
|Dairy products||0.000 (0%)||0.002 (8%)|
|Snack||0.000 (0%)||0.000 (2%)|
41. The 95th percentile exposure level of the secondary school students was used to represent the dietary exposure to 1,3-DCP for a high consumer and was estimated to be 0.009 – 0.040 m g/kg bw/day .
Dietary exposure estimates from sauces
42. According to the literature, the main dietary sources of 3-MCPD for the general population, particularly in Asian, are soya sauce and oyster sauce. Dietary exposures to 3-MCPD from soya sauce and oyster sauce were therefore estimated based on the assumptions stated below.
Levels of 3-MCPD in soya sauce and oyster sauces
43. Previous joint studies conducted by the FEHD and the Consumer Council revealed that the average level of 3-MCPD in soya sauce ranged from 7 m g/kg (lower bound) to 16 m g/kg (upper bound) with a highest reported level of 260 m g/kg and that in oyster sauce ranged from 3 m g/kg (lower bound) to 5 m g/kg (upper bound) with a highest reported level of 29 m g/kg.7, 8
Food consumption pattern for sauces
44. D ata on the consumption pattern for sauces and condiments is limited in Hong Kongc. JECFA once reported that the per-capita consumption of soya sauce in Japan was about 30 g per person per day (which has been considered to be overestimated) whilst an email communication with National Food Research Institute in Japan indicated that the soya sauce sold to the Japanese market in 2001 was 771 286 kilolitres (i.e., ~ 17 millilitres per person per day). In the Mainland, it was reported that the average consumption of soya sauce for people
resided in the urban area was 10.7 g/day in 2002.12
45. As the consumption pattern for oyster sauce is not available, it is assumed that its consumption pattern would be about half of that for soya sauce.
46. The resulting average dietary exposure of 3-MCPD of a 52-kg secondary school student upon consumption of soya sauce and oyster sauce are estimated using the average levels of 3-MCPD in soya sauce and oyster sauce. The possible dietary exposure to 3-MCPD for those consumers who are loyal to particular brand of products was estimated using the highest reported levels of 3-MCPD in soya sauce and oyster sauce. (Table 6)
Table 6. Dietary Exposure to 3-MCPD from Soya Sauce and Oyster Sauce of a 52-kg Secondary School Student ( m g/kg bw/day) (%PMTDI)
|Average exposure||Highest Exposure for consumer of particular brand of product|
|Lower bound||Upper bound|
Scenario 1 -
Soya sauce: 30 g
Oyster sauce: 15 g
|0.005 (0.2%)||0.011 (0.5%)||0.158 (7.9%)|
Scenario 2 -
Soya sauce: 10.7 g
Oyster sauce: 5.4 g
|0.002 (0.1%)||0.004 (0.2%)||0.057 (2.8%)|
47. Even under the most extreme scenario, i.e., a 52-kg secondary school student who was loyal to a particular brand of product and consumed 30 g soya sauce and 15 g oyster sauce per day, the resulting exposure to 3-MCPD was estimated to be 0.158 m g/kg bw/day, which amounted to less than 8% of the PMTDI.
48. In this study, the average exposure estimates under scenario 1 would be combined with those from foods other than soya and oyster sauces to give a rough estimates of the overall exposures to 3-MCPD from the diet (see para. 50). These values were likely to be overestimated as the highest reported consumption pattern of sauces was used under scenario 1.
49. Soya sauce has been considered as one of the main dietary source of 1,3-DCP for the general population who consumes soya sauce. However, the dietary exposure to 1,3-DCP due to sauce consumption could not be estimated d ue to the lack of data on 1,3-DCP in soya sauce in Hong Kong .
Overall exposure to 3-MCPD
50. The dietary exposure to 3-MCPD for the average and high consumers of secondary school student was estimated to be 0.063 – 0.150 m g/kg bw/day and 0.152 – 0.300 m g/kg bw/day respectively (Table 7).
Table 7: Comparison between PMTDI Established by JECFA and Overall Dietary Exposures to 3-MCPD for Average and High Consumers of Secondary School Students ( m g/kg bw/day) (% of PMTDI)
|Sources of exposure||Average consumer||High consumer|
|Foods other than sauces||0.058 to 0.139||0.147 to 0.289|
|Soya sauce and oyster sauce||0.005 to 0.011||0.005 to 0.011|
|Overall exposure||0.063 (3%) to 0.150 (8%)||0.152 (8%) to 0.300 (15%)|
51. The dietary exposure to 3-MCPD for an average consumer of secondary school student was estimated to be 0.063 – 0.150 m g/kg bw/day whilst that for the high consumer was 0.152 – 0.300 m g/kg bw/day. These exposures amounted to 3 – 8 % and 8 – 15 % of the PMTDI respectively. Exposures to 3-MCPD for both average and high consumers of secondary school student fell below the PMTDI established by JECFA.
52. The above dietary exposure estimates therefore suggested the average and high consumers of secondary school students were unlikely to experience major toxicological effects of 3-MCPD .
Major dietary sources
53. In this study, the main dietary source of 3-MCPD was "cereal and their products" and this was followed by "meat, poultry and their products". Even though sauces have been previously reported to be the main dietary source of 3-MCPD, it only contributed to 3-17% of the overall dietary exposure in this study, and its dietary exposure estimate was lower than those from "cereal and their products" and "meat, poultry and their products".
54. Among those "foods other than sauces" with detectable amount of 3-MCPD, instant noodle was the largest contributor to total dietary exposure to 3-MCPD, i.e., 0.012 m g/kg bw/day, which was higher than those contributed by soya sauce and oyster sauce. This might be due to its relatively high level of 3-MCPD (average: 18 m g/kg) and consumption pattern as well as the fact that the soup base for instant noodle might contain acid-HVP as a savoury ingredient. As the dietary exposure to 3-MCPD upon consumption of instant noodle soup had not been taken into account in this study, the exposure is expected to be higher for those consumers of the instant noodle soup.
55. On the other hand, besides soya sauce, seaweed under the food group "snack" had the highest reported concentration of 3-MCPD (average: 56 m g/kg). However, its relatively low consumption pattern made it accountable for less than 1% of total dietary exposure to 3-MCPD. Ready-to-eat seaweed may contain acid-HVP as a savoury ingredient.
56. The dietary exposure to 1,3-DCP for an average consumer of secondary school student was estimated to be 0.003 – 0.019 m g/kg bw/day whilst that for the high consumer was 0.009 – 0.040 m g/kg bw/day. The resulting MOEs for an average consumer ranged from 174 000 to 1 100 000 whereas those for high consumers ranged from 84 000 to 355 000, taking into account the BMDL 10 value of 3.3 mg/kg bw/day (Table 8). Such MOE values suggested that the estimated exposures to 1,3-DCP for both average and high consumers of secondary school students were of low concern for human health.
Table 8: MOEs for Dietary Exposures to 1,3-DCP for Average and High Consumers of Secondary School Students
|BMDL 10 (mg/kg bw/day)||Average consumer||High consumer|
|3.3||174 000 – 1 100 000
|84 000 – 355 000
Major dietary sources
57. In this study, the main dietary sources of 1,3-DCP at the lower bound was "meat, poultry and their products" and that at the upper bound was "cereal and their products". Nevertheless, it should be noted that 1,3-DCP was not detected in any food items under the food group "cereal and their products". The high consumption pattern for "cereal and their products" and the low concentration in other detected items probably made "cereal and their products" the main contributor at upper bound estimate. On the other hand, the LOD for 1,3-DCP might also affect the dietary exposure estimates. However, the LOD for 1,3-DCP adopted in our study was comparable to those used by authorities in the international arena for dietary exposure assessment and was in fact lower than the one adopted in Australia .
58. For the food group "meat, poultry and their products", only two food items, namely sausage and roast pork, were detected with 1,3-DCP. Even though roast pork has the highest level of 1,3-DCP (average: 9.3 m g/kg), its relatively small amount of consumption made sausage the largest contributor, i.e., 11% (upper bound) to 67% (lower bound) of the total dietary exposure. Unlike the results of other overseas studies, 1,3-DCP was not detected in any minced beef and ham samples in this study.4
59. Studies on dietary exposures to 3-MCPD and 1,3-DCP conducted overseas were reviewed and summarised in Table 9.
Table 9. A Comparison of Average Daily Exposure to 3-MCPD and 1,3-DCP ( m g/kg bw/day)
|Australia 6||0.16-0.20 *||0.012-0.041 *|
|Denmark 5||0.101 *||NA|
|Finland 5||0.200 *||NA|
|France 5||0.107 *||NA|
|Hong Kong||0.063-0.150†||0.003-0.019 †|
|Ireland 5||0.196 *||NA|
|Netherlands 5||0.158 *||NA|
|Sweden 5||0.047 *||NA|
* Estimated dietary exposure to 3-MCPD from various food sources, including soya and oyster sauces.
† The exposure data in Hong Kong is extracted from our current study.
‡ The data was derived from the total diet study in 2001 with no clear indication whether the exposure from sauces and related products was included.
NA denotes not available.
60. It can be seen that dietary exposure to 3-MCPD estimated in our study is about the same order of magnitude when compared to exposure estimates obtained from overseas studies whereas that for 1,3-DCP (without taken into account the 1,3-DCP exposure from sauces) is lower than the Australian study. This comparison gives the reader a rough idea of the local situation relative to the international picture, but it should be noted that direct comparison of data between different studies has to be done with caution due to the differences in time when the studies were carried out, research methodology, food group categorisation (particularly whether the exposures from sauces and condiments were included), methods of collection of consumption data, methods of chloropropanols analyses and methods of treating results below the detection limits.
LIMITATION OF THE EXPOSURE ASSESSMENT STUDY
61. The methodology for collecting food consumption data may influence the accuracy of the estimates on dietary exposure. In the Food Consumption Survey, the food consumption pattern of secondary school students was collected using a food frequency questionnaire. Although the questionnaire was very comprehensive, it was not possible to cover every single food item, some of which might be relevant to exposure to chloropropanols, particularly sauces and condiments, instant noodle soup, etc. Furthermore, only the data of consumption pattern for secondary school students is available.
62. Three samples for each food item were collected for laboratory analysis. Although about 300 samples were taken in this study, increasing the number of sample for each food item for laboratory analysis could provide a more precise estimate of the average concentrations of 3-MCPD and 1,3-DCP for a particular food item. However, the number of samples taken have to be balanced with the required resources and number of food items to be included.
63. On the other hand, the assessment of dietary exposure to 1,3-DCP was not comprehensive in this study because of the lack of data on the level of 1,3-DCP in sauces.
CONCLUSION AND RECOMMENDATION
64. The dietary exposure to 3-MCPD for an average consumer of secondary school student was estimated to be 0.063 – 0.150 m g/kg bw/day whilst that for the high consumer was 0.152 – 0.300 m g/kg bw/day. Both estimates fell below the safety reference value (i.e., < 20% of the PMTDI) established by JECFA. It could be concluded that both the average and high consumers of the secondary school students were unlikely to experience major toxicological effects of 3-MCPD.
65. The food group "cereal and their products", particularly instant noodle, was identified as the main dietary source of 3-MCPD.
66. The dietary exposure to 1,3-DCP for an average consumer of secondary school student was estimated to be 0.003 – 0.019 m g/kg bw/day whilst that for the high consumer was 0.009 – 0.040 m g/kg bw/day. The resulting MOEs were of low concern for human health.
67. Among the food groups with detected amount of 1,3-DCP, the food group "meat, poultry and their products", particularly sausage, was identified as the main dietary source of 1,3-DCP.
68. Results of our previous studies and routine surveillance programme indicated the local trade has put much effort in reducing the levels of chloropropanols in sauces and condiments since 1999. Nevertheless, the trade is advised to continue observing good manufacturing practice and reducing the levels of chloropropanols in food as far as is technically achievable. Generally speaking, there are three main approaches in minimising the formation of 3-MCPD in acid-HVP: (i) careful control of the acid hydrolysis step; (ii) subsequent neutralisation to minimise 3-MCPD formation; and (iii) the use of sulphuric acid instead of hydrochloric acid during the hydrolysis.14
69. Codex is currently developing a Code of Practice for the Reduction of 3-MCPD during the Production of Acid-HVPs and Products that Contain Acid-HVPs.15 Even though the intake estimates indicate that 3-MCPD and 1,3-DCP are not of immediate health concern, further research studies by the industries and academia deem necessary to explore the exact mechanisms for the formation of chloropropanols in other foods that do not contain acid-HVP and to propose ways to further reduce the levels of these contaminants.
70. The public is advised to maintain a balanced diet so as to avoid excessive exposure to chemical contaminants from a small range of food items.
1 UK Ministry of Agriculture, Fisheries and Food (MAFF). Survey of 3-monochloropropan-1,2-diol (3-MCPD) in soya sauce and similar products. Joint Food Safety and Standard Groups Food Surveillance Information Sheets Number 187. London : MAFF; September 1999. Available from: URL: http://archive.food.gov.uk/maff/archive/food/infsheet/1999/no187/187soy.htm
2 WHO. 3-Chloro-1,2-propanediol. Safety evaluation of certain food additives and contaminants: WHO food additives series: 48. Geneva : WHO; 2001. [cited 30 Jan 07] Available from: URL: http://www.inchem.org/documents/jecfa/jecmono/v48je18.htm
3 WHO. 1,3-Dichloro-2-propanol. Safety evaluation of certain food additives and contaminants: WHO food additives series: 48. Geneva : WHO; 2001. [cited 30 Jan 07] Available from: URL: http://www.inchem.org/documents/jecfa/jecmono/v48je19.htm
4 Joint FAO/WHO Food Standards Programme – Codex Committee on Contaminants in Food. Discussion paper on chloropropanols derived from the manufacture of acid-HVP and the heat processing of foods. CX/CF 07/1/13 . Rome : Codex Alimentarius Commission; February 2007.
5 European Commission Directorate-General Health and Consumer Protection. Report of experts participating in Task 3.2.9 - collection and collation of data on levels of 3-monochlorpropanodiol (3-MCPD) and related substances in foodstuffs. Brussels ; European Commission; June 2004. Available from: URL: http://ec.europa.eu/food/food/chemicalsafety/contaminants/mcpd_en.htm
6 Food Standards Australia New Zealand (FSANZ). Chloropropanols in food – an analysis of the public health risk. Technical report series no. 15. Canberra ; FSANZ; October 2003. Available from: URL: http://www.foodstandards.gov.au/newsroom/technicalreportserie1338.cfm
7 Consumer Council and FEHD. 3 soya sauce products having contaminant 3-MCPD. Choice, Issue 310, p. 22-27; October 2002. Available from: URL: http://www.cfs.gov.hk/english/programme/programme_rafs/programme_rafs.html
8 Consumer Council and FEHD. 3-MCPD in condiments and sauces. Choice, Issue 329, p. 22-27; March 2004. Available from: URL: http://www.cfs.gov.hk/english/programme/programme_rafs/programme_rafs.html
9 JECFA. Sixty-seventh meeting – summary and conclusions. Rome : FAO; July 2006. Available from: URL: http://www.who.int/ipcs/food/jecfa/summaries/summary67.pdf
10 FEHD. Food Consumption Survey 2000. Hong Kong : FEHD; 2001.
11 WHO. GEMS/Food-EURO Second Workshop on reliable evaluation of low-level contamination of food – report of a workshop in the frame of GEMS/Food-EURO. WHO; May 1995. Available from: URL: http://www.who.int/foodsafety/publications/chem/lowlevel_may1995/en/index.html
12 中華人民共和國衞生部 , 中華人民共和國科學技術部 , 中華人民共和國國家統計局 . 中國居民營養與健康現狀 . Beijing : Chinese Center for Disease Control and Prevention; 2004. Available from: http://www.chinacdc.net.cn/n272442/n272530/n273736/n273812/n293881/n293888/3748.html
13 UK Food Standard Agency (FSA) Analysis of 3-monochlorpropane-1,2-diol (3-MCPD) in the UK diet: 2001 total diet study. Food Survey Information Sheet 75/05. London : FSA; September 2005. Available from: URL: http://www.food.gov.uk/science/surveillance/fsis2005/fsis7505
14 Joint FAO/WHO Food Standards Programme – Codex Committee on Contaminants in Food. Proposed draft code of practice for the reduction of 3-monchlorpropane-1,2-diol (3-MCPD) during the production of acid-hydrolysed vegetable proteins (Acid-HVPs) and products that contain acid-HVPs. CX/CF 07/1/14. Rome: Codex Alimentarius Commission; January 2007.
a The benchmark dose lower confidence limit (BMDL) is the lower one-sided confidence limit of the benchmark dose (BMD) for a predetermined level of response (usually for the carcinogenic response(s) of relevance to human health), called the benchmark response (BMR), such as a 5 or 10% incidence. It can be used as a starting point for hazard characterization for chemical that is genotoxic and carcinogenic and when the available data are suitable for dose-response modelling.
b Margin of exposure ( MOE) is the ratio of the BMDL to the estimated intake of a compound in humans. It is used to prioritise different contaminants that are genotoxic and carcinogenic for further risk management.
c According to Hong Kong Merchandise Trade Statistics reported by the Census and Statistics Department of HKSARG, 2,336,281 kg of soya sauce was imported and 372,922 kg was exported/re-exported from Hong Kong . However, the exact consumption pattern for soya sauce or the amount of soya sauce available for retail in Hong Kong is not available, due to the lack of data on the volume of local production.
Levels of 3-MCPD and 1,3-DCP in Individual Food Items
|Food Group||Food Item||Number of Samples||3-MCPD ( m g/kg)||1,3-DCP ( m g/kg)|
|Number of detects||Range||Number of detects||Range|
Cereal and their products
|Flatten noodle||3||2||< LOD – 9||0||-|
|Instant noodle||3||3||14 – 23||0||-|
|Bread, white||3||3||8 – 13||0||-|
|Bread, wheat||3||3||11 – 23||0||-|
|Plain roll||3||3||10 – 20||0||-|
|Sausage roll||3||3||9 – 10||0||-|
|Sweet roll||3||2||< LOD – 8||0||-|
|Soda cracker||3||3||17 – 22||0||-|
|Spring onion cracker||3||0||-||0||-|
|Paper wrapped cake||3||3||4 – 8||0||-|
|Egg tart||3||3||8 – 14||0||-|
|Hamburger||3||3||11 – 20||0||-|
Vegetable and their products
Fish, shellfish and their products
|Golden thread, steamed||3||0||-||0||-|
|Golden thread, shallow-fried||3||0||-||0||-|
|Sole fillet, steamed||3||0||-||0||-|
|Sole fillet, shallow-fried||3||0||-||0||-|
|Mud carp / dace, minced, steamed||3||0||-||0||-|
|Mud carp / dace, minced, shallow-fried||3||0||-||0||-|
|Green grouper, steamed||3||0||-||0||-|
|Japanese eel, grilled||3||3||7 – 33||0||-|
|Salmon fillet, shallow-fried||3||3||5 – 7||0||-|
|Shrimp meat, shallow-fried||3||0||-||0||-|
|Crab, steamed||3||3||3 – 9||3||3.5 – 5.0|
|Crab, stir-fried||3||3||3 – 10||3||2.5 – 6.0|
|Salted fish, steamed||3||3||9 – 21||3||3.0 – 3.5|
|Marinated octopus / cuttlefish / squid||3||0||-||0||-|
|Other octopus / cuttlefish, squid, cooked||3||0||-||0||-|
Meat, poultry and their products
|Pork, shredded, steamed||3||0||-||0||-|
|Pork, shredded, stir-fried||3||3||6 – 9||0||-|
|Pork, minced, steamed||3||0||-||0||-|
|Pork, minced, stir-fried||3||3||9 – 15||0||-|
|Beef, shredded, steamed||3||3||5 – 9||0||-|
|Beef, shredded, stir-fried||3||3||9 – 32||0||-|
|Beef, minced, steamed||3||1||< LOD – 4||0||-|
|Beef, minced, stir-fried||3||3||9 – 14||0||-|
|Barbequed pork||3||3||6 – 28||0||-|
|Roasted pork||3||3||6 – 19||3||9.0 – 9.5|
|Roasted duck / goose||3||2||< LOD – 7||0||-|
|Marinated duck / goose||3||3||11 – 14||0||-|
|Pork liver, cooked||3||2||< LOD – 14||0||-|
|Other pig's offal, cooked||3||0||-||0||-|
|Marinated beef tripe||3||0||-||0||-|
|Marinated beef lights||3||0||-||0||-|
|Marinated beef milt||3||0||-||0||-|
|Marinated beef intestine||3||0||-||0||-|
|Beef ball||3||3||4 – 6||0||-|
|Luncheon meat||3||2||< LOD – 9||0||-|
|Ham||3||2||0 – 22||0||-|
|Sausage||3||0||-||3||4.5 – 5.0|
|Big red sausage||3||1||0 – 27||0||-|
|Liver sausage||3||3||5 – 10||0||-|
|Preserved pork||3||3||9 – 15||0||-|
Egg and their products
|Egg white, steamed||3||0||-||0||-|
|Egg white, fried||3||0||-||0||-|
|Egg yolk, steamed||3||0||-||0||-|
|Egg yolk, fried||3||0||-||0||-|
|Limed duck egg||3||0||-||0||-|
|Salted duck egg||3||0||-||0||-|
|Potato chips||3||3||6 – 11||0||-|
|Prawn crackers||3||3||25 – 33||0||-|
|Seaweed, ready-to-eat||3||3||50 – 66||0||-|
LODs for 3-MCPD and 1,3-DCP were 2.5 μ g/kg (ppb) and 0.5 μ g/kg (ppb) respectively.