PAH contamination in shellfish: modelling to estimate exposure.

Polycyclic aromatic hydrocarbons (PAH) are known carcinogens and are abundant in the environment and foodstuffs. Currently the majority of PAH research focuses on benzo[a]pyrene (BaP), although a much greater range of PAH are known to have detrimental effects to human health. Monitoring a large number of PAH is expensive, time consuming and analytically demanding, yet there is currently no clear basis for determining which PAH should be monitored to give an indication of overall exposure. A thorough statistical examination of the relationships between different PAH in different foodstuffs has not previously been carried out. Using a test dataset of homogenised edible flesh from shellfish samples as a case study a modelling process using principal components analysis regression is proposed to determine which PAH subset (from a total of 27 monitored PAH) should be assessed as indicators for general PAH exposure. Multivariate ordination and clustering show that PAH concentrations of compounds of similar chemical structure can be highly correlated in the samples, e.g. the five ringed isomers PAHs benzo[b]fluoranthene, benzo[j]fluoranthene and benzo[k]fluoranthene. The model selection process determined which subsets of PAH can be used to predict the presence and abundance of other PAHs in shellfish samples. Models were more accurate in predicating PAHs concentrations of PAH where concentrations were measured above the limit of detection (LoD). PAH with values below the LoD were harder to predict accurately. The current analysis highlights that laboratories should focus on the following PAHs BaP, benzo[a]anthracene, benzo[g,h,i]perylene, phenanthrene, benzo[g,h,i]fluoranthene, chrysene, benzo[k]fluoranthene, benzo[b]fluoranthene and fluoranthene when analysing shellfish samples. Focussing monitoring on this group of PAH may give a better indication of overall PAH content of samples that the summed PAH indicator methods currently adopted.

Validation of three rapid screening methods for detection of verotoxin-producing Escherichia coli in foods: interlaboratory study.

An interlaboratory study was conducted for the validation of 3 methods for the detection of all verotoxin-producing Escherichia coli (VTEC) in foods. The methods were a multi-analyte 1-step lateral flow immunoassay (LFIA) for detection of E. coli O157 and verotoxin (VT); an enzyme-linked immunosorbent assay targeted against VT1, VT2, and VT2c (VT-ELISA); and a polymerase chain reaction (PCR) method for detection of VT genes (VT-PCR). Aliquots (25 g or 25 mL) of 4 food types (raw minced [ground] beef, unpasteurized milk, unpasteurized apple juice [cider], and salami) were individually inoculated with low numbers (<9 to 375 cells/25 g) of 6 test strains of E. coli (serogroups O26, O103, O111, O145, and O157) with differing VT-producing capabilities. Five replicates for each test strain and 5 uninoculated samples were prepared for each food type. Fourteen participating laboratories analyzed samples using the LFIA, 9 analyzed the samples by ELISA, and 9 by PCR. The LFIA for O157 and VT had a specificity (correct identification of negative samples) of 92 and 94%, respectively, and a sensitivity (correct identification of positive samples) of 94 and 55%, respectively. The VT-ELISA and VT-PCR had a specificity of 98 and 99%, respectively, and a sensitivity of 89 and 72%, respectively.