Handling of contamination variability in exposure assessment: A case study with ochratoxin A

Probabilistic dietary exposure to phycotoxins in a recreational shellfish harvester subpopulation (France)

Phycotoxins, secondary phytoplankton metabolites, are considered as an important food safety issue because their accumulation by shellfish may render them unfit for human consumption. However, the likely intakes of phycotoxins via shellfish consumption are almost unknown because both contamination and consumption data are very scarce. Thus, two 1-year surveys were conducted (through the same population: recreational shellfish harvesters and from the same geographical area) to assess: shellfish consumption and contamination by major toxins (domoic acid (DA) group, okadaic acid (OA) group and spirolides (SPXs)). Recreational shellfish harvesters had been targeted as an at-risk subpopulation because they consume more shellfish than general population and because they eat not only commercial shellfish species controlled by official authorities but also their own harvests of shellfish species may be in non-controlled areas and more over shellfish species non-considered in the official control species. Then, these two kinds of data were combined with deterministic and probabilistic approaches for both acute and chronic exposures, on considering the impact of shellfish species and cooking on phycotoxin levels. For acute risk, monitoring programs seem to be adequate for DAs, whereas OAs could be a matter of concern for high consumers (their acute intakes were up to ninefold the acute reference dose (ARfD)). About chronic risk, OAs are a matter of concern. The daily OAs intakes were close to the ARfD, which is, by definition, greater than the tolerable daily intake. Moreover, SPX contamination is low but regular, no (sub)chronic SPX toxicity data exist; but in case of (sub)chronic toxicity, SPX exposure should be considered.

A review of contemporary methods for the presentation of scientific uncertainty

Graphic methods for displaying uncertainty are often the most concise and informative way to communicate abstract concepts. Presentation methods currently in use for the display and interpretation of scientific uncertainty are reviewed. Numerous subjective and objective uncertainty display methods are presented, including qualitative assessments, node and arrow diagrams, standard statistical methods, box-and-whisker plots,robustness and opportunity functions, contribution indexes, probability density functions, cumulative distribution functions, and graphical likelihood functions.

Application of isotope dilution mass spectrometry: determination of ochratoxin A in the Canadian Total Diet Study

Analytical methods are generally developed and optimized for specific commodities. Total Diet Studies, representing typical food products 'as consumed', pose an analytical challenge since every food product is different. In order to address this technical challenge, a selective and sensitive analytical method was developed suitable for the quantitation of ochratoxin A (OTA) in Canadian Total Diet Study composites. The method uses an acidified solvent extraction, an immunoaffinity column (IAC) for clean-up, liquid chromatography-tandem mass spectrometry (LC-MS/MS) for identification and quantification, and a uniformly stable isotope-labelled OTA (U-[(13)C(20)]-OTA) as an internal recovery standard. Results are corrected for this standard. The method is accurate (101% average recovery) and precise (5.5% relative standard deviation (RSD)) based on 17 duplicate analysis of various food products over 2 years. A total of 140 diet composites were analysed for OTA as part of the Canadian Total Diet Study. Samples were collected at retail level from two Canadian cities, Quebec City and Calgary, in 2008 and 2009, respectively. The results indicate that 73% (102/140) of the samples had detectable levels of OTA, with some of the highest levels of OTA contamination found in the Canadian bread supply.

Occurrence of aflatoxin M₁ and exposure assessment in Catalonia (Spain)

BACKGROUND

Aflatoxin M₁ (AFM₁) is the main monohydroxylated derivative of aflatoxin B₁ (AFB₁) formed in liver and excreted into milk. Although AFM₁ is less toxic than AFB₁, it has been classified as a possible human carcinogen, Group 2B agent by International Agency for Research on Cancer (IARC).

OBJECTIVES

The objectives of this study were (i) to determine the occurrence of AFM₁ in the main dairy products consumed in Catalonia region (Spain), and (ii) to assess the exposure of Catalonian population to aflatoxin M₁ through deterministic and probabilistic method.

METHODS

Occurrence of Aflatoxin M₁ (AFM₁) was determined in 72 composites of milk, 72 composites of cheese and 72 composites of yoghurt from Catalonia. AFM₁ content was analysed using an Enzyme-Linked ImmunoSorbent Assay commercial kit. Three approaches to exposure assessment were conducted: one deterministic method and two probabilistic models with Monte Carlo simulations.

RESULTS

AFM₁ was detected in 94.4% (68/72) of whole UHT milk samples, in 2.8% (2/72) of yoghurt samples and not detected in cheese. The maximum level was detected in one yoghurt sample with 51.58 ng/kg, only this sample being over the legal EU limit of 50 ng/kg. Milk, cheese and yoghurt mean concentrations were 9.29±2.61, <12.5 and 13.22±4.82 ng/kg, respectively.

CONCLUSIONS

According to these values, it should be expected Catalonian population is not exposed to a significant risk from aflatoxin M₁ including average and high consumers.

Health risk assessment of ochratoxin A for all age-sex strata in a market economy

In order to manage risk of ochratoxin A (OTA) in foods, we re-evaluated the tolerable daily intake (TDI), derived the negligible cancer risk intake (NCRI), and conducted a probabilistic risk assessment. A new approach was developed to derive 'usual' probabilistic exposure in the presence of highly variable occurrence data, such as encountered with low levels of OTA. Canadian occurrence data were used for various raw food commodities or finished foods and were combined with US Department of Agriculture (USDA) food consumption data, which included data on infants and young children. Both variability and uncertainty in input data were considered in the resulting exposure estimates for various age/sex strata. Most people were exposed to OTA on a daily basis. Mean adjusted exposures for all age-sex groups were generally below the NCRI of 4 ng OTA kg bw(-1), except for 1-4-year-olds as a result of their lower body weight. For children, the major contributors of OTA were wheat-based foods followed by oats, rice, and raisins. Beer, coffee, and wine also contributed to total OTA exposure in older individuals. Predicted exposure to OTA decreased when European Commission maximum limits were applied to the occurrence data. The impact on risk for regular eaters of specific commodities was also examined.

Fitness-for-purpose of dietary survey duration: a case-study with the assessment of exposure to ochratoxin A

The duration of food consumption survey may have a marked effect on estimates of usual nutrient intakes in individuals and groups. This arises from a high degree of within-person variability in food intakes, primarily on a day-to-day basis. Both the level of observation-populations versus individuals-and the desirable level of precision decide upon the 'fitness-for-purpose' of dietary survey duration. Though similar from a methodological standpoint, the question was rarely addressed in the case of non-nutrients. Our work aims at estimating the number of days of food records needed for the assessment of usual intakes of food chemicals as a function of research purpose. Focusing on the French population exposure to food mycotoxin ochratoxin A, we implement a range of well-established methods borrowed from the field of nutrient intakes assessment. Our results on OTA show that: (a) at the population level, as low as three days give satisfactory distributional estimates; yet, the implementation of variance reduction methods is of particular relevance when higher percentiles of exposure are at stake; (b) the estimation of individual usual intakes based on food records is behind practical possibilities, which calls for alternative options such as biomarkers of exposure.