Detection of trace aflatoxin M1 in human urine using a commercial ELISA followed by HPLC

Infant exposure to ochratoxin A, zearalenone, and deoxynivalenol from the consumption of milk formula and baby cereal in Chile

Ochratoxin A (OTA), zearalenone (ZEN), and deoxynivalenol (DON) are mycotoxins whose exposure is associated with various adverse health effects, including cancer and renal disorders, estrogenic effects, and immunosuppressive and gastrointestinal disorders, respectively. Infants (<2 years) are the most vulnerable group to mycotoxins, representing a unique combination of restricted food consumption types, low body weight, lower ability to eliminate toxins, and more future years to accumulate toxins. This study aimed to estimate the infant́s exposure to OTA, DON, and ZEN due to the consumption of milk formula and baby cereals in Chile. Milk formula samples (n = 41) and baby cereals (n = 30) were collected and analyzed using commercial ELISA kits for OTA, DON, and ZEA determination. Exposure was assessed by the Estimated Daily Intake (EDI) approach (mean and worst-case scenario, WCS) with the levels found in a modified Lower Bound (mLB) and Upper Bound (UB); ideal consumption (<6m, 7-12 m, and 13-24 m); adjusted by the weight of each group. The risk was estimated by comparing the EDI with a reference tolerable daily intake or by the margin of exposure (MOE) in the case of OTA. DON and OTA occurrence in infant formula were 34 % and 41 %, respectively. The co-occurrence between these mycotoxins was 22 %. Mycotoxin contents were below LOQ values except for OTA determined in one sample (0.29 ng/ml). No milk formulae were contaminated with ZEN. In the case of baby cereals, the occurrences were 17 % for OTA, 30 % for DON, and 7 % for ZEN, all below LOQ. Co-occurrence was seen in two samples between ZEN and OTA. According to exposure calculations, the MOE for OTA was less than 10,000 in all models for milk formula between 0 to 12 months of age and in the UB and WCS for cereal consumption. Health concerns were observed for DON in the WCS and UB for milk consumption in all ages and only in the UB WCS for cereal consumption. Considering the high consumption of milk formula in these age groups, regulation of OTA and other co-occurring mycotoxins in infant milk and food is strongly suggested.

Literature review and evaluation of biomarkers, matrices and analytical methods for chemicals selected in the research program Human Biomonitoring for the European Union (HBM4EU)

Humans are potentially exposed to a large amount of chemicals present in the environment and in the workplace. In the European Human Biomonitoring initiative (Human Biomonitoring for the European Union = HBM4EU), acrylamide, mycotoxins (aflatoxin B1, deoxynivalenol, fumonisin B1), diisocyanates (4,4'-methylenediphenyl diisocyanate, 2,4- and 2,6-toluene diisocyanate), and pyrethroids were included among the prioritized chemicals of concern for human health. For the present literature review, the analytical methods used in worldwide biomonitoring studies for these compounds were collected and presented in comprehensive tables, including the following parameter: determined biomarker, matrix, sample amount, work-up procedure, available laboratory quality assurance and quality assessment information, analytical techniques, and limit of detection. Based on the data presented in these tables, the most suitable methods were recommended. According to the paradigm of biomonitoring, the information about two different biomarkers of exposure was evaluated: a) internal dose = parent compounds and metabolites in urine and blood; and b) the biologically effective = dose measured as blood protein adducts. Urine was the preferred matrix used for deoxynivalenol, fumonisin B1, and pyrethroids (biomarkers of internal dose). Markers of the biological effective dose were determined as hemoglobin adducts for diisocyanates and acrylamide, and as serum-albumin-adducts of aflatoxin B1 and diisocyanates. The analyses and quantitation of the protein adducts in blood or the metabolites in urine were mostly performed with LC-MS/MS or GC-MS in the presence of isotope-labeled internal standards. This review also addresses the critical aspects of the application, use and selection of biomarkers. For future biomonitoring studies, a more comprehensive approach is discussed to broaden the selection of compounds.

A preliminary study on aflatoxin exposure by urine biomonitoring in Chile

We assessed the occurrence of aflatoxin M₁ (AFM₁) in urine in a sample of the MAUCO population-based cohort (n = 120) using an enzyme-linked immune sorbent assay (ELISA) kit specially designed for the analysis of AFM₁ in urine. We found AFM₁ in the urine of 59% of the participants (> limit of detection), with 12% of the samples being over the limit of quantification. The mean of the quantifiable samples was 0.66 (± 0.35) ng/mg adjusted creatinine, ranging from 0.31 to 1.39 ng/mg creatinine. The mean probable daily intake (PDI) of AFB₁ was 0.23 (± 0.37) ng/kg bw according to the upper bound (UB), being significantly higher in women and 0.14 (± 0.23) ng/kg bw in the modified lower bound (mLB) approach, ranging from 0.01 to 1.98 ng/kg bw. The risk of AFB₁ was assessed with the margin of exposure (MOE) approach estimated at 2800 in the mean mLB and 1733 in the mean UB. According to the MOE values obtained in this study, aflatoxin B₁ exposure must be considered a public health concern and must be taken as a priority for food risk management.

Risk assessment of aflatoxins in food

EFSA was asked to deliver a scientific opinion on the risks to public health related to the presence of aflatoxins in food. The risk assessment was confined to aflatoxin B1 (AFB1), AFB2, AFG1, AFG2 and AFM1. More than 200,000 analytical results on the occurrence of aflatoxins were used in the evaluation. Grains and grain-based products made the largest contribution to the mean chronic dietary exposure to AFB1 in all age classes, while 'liquid milk' and 'fermented milk products' were the main contributors to the AFM1 mean exposure. Aflatoxins are genotoxic and AFB1 can cause hepatocellular carcinomas (HCCs) in humans. The CONTAM Panel selected a benchmark dose lower confidence limit (BMDL) for a benchmark response of 10% of 0.4 μg/kg body weight (bw) per day for the incidence of HCC in male rats following AFB1 exposure to be used in a margin of exposure (MOE) approach. The calculation of a BMDL from the human data was not appropriate; instead, the cancer potencies estimated by the Joint FAO/WHO Expert Committee on Food Additives in 2016 were used. For AFM1, a potency factor of 0.1 relative to AFB1 was used. For AFG1, AFB2 and AFG2, the in vivo data are not sufficient to derive potency factors and equal potency to AFB1 was assumed as in previous assessments. MOE values for AFB1 exposure ranged from 5,000 to 29 and for AFM1 from 100,000 to 508. The calculated MOEs are below 10,000 for AFB1 and also for AFM1 where some surveys, particularly for the younger age groups, have an MOE below 10,000. This raises a health concern. The estimated cancer risks in humans following exposure to AFB1 and AFM1 are in-line with the conclusion drawn from the MOEs. The conclusions also apply to the combined exposure to all five aflatoxins.

Quantum bead-based fluorescence-linked immunosorbent assay for ultrasensitive detection of aflatoxin M1 in pasteurized milk, yogurt, and milk powder

Herein, we reported a novel direct competitive fluorescence-linked immunosorbent assay (dcFLISA) for the ultrasensitive detection of aflatoxin M₁ (AFM₁) in pasteurized milk, yogurt, and milk powder using 150-nm quantum dot beads (QB) as the carrier of competing antigen. Large QB were applied to decrease the binding affinity of the competing antigen to antibody and enhance the fluorescent signal intensity. The aflatoxin B₁ molecule was used as the surrogate of AFM₁ to label with BSA on the surface of QB because of its 63% cross reaction to anti-AFM₁ mAb. The binding affinity of the competing antigen to mAb was tuned by changing the labeled molar ratios of aflatoxin B₁ to BSA. Through combining the advantages of QB as the carrier of the competing antigen, including low binding affinity to mAb and highly fluorescent signal output, the proposed dcFLISA exhibited an ultrahigh sensitivity for AFM₁ detection, with a half-maximal inhibitory concentration of 3.15 pg/mL in 0.01 M phosphate-buffered saline solution (pH 7.4), which is substantially lower than that of the traditional horseradish peroxidase-based ELISA. The proposed method also exhibited very low detection limitations of 0.5, 0.6, and 0.72 pg/mL for real pasteurized milk, yogurt, and milk powder, respectively. These values are considerably below the maximum permissible level of the European Commission standard for AFM₁ in dairy products. In summary, the proposed dcFLISA offers a novel strategy with an ultrahigh sensitivity for the routine monitoring of AFM₁ in various dairy products.

Comparison of urinary aflatoxin M1 and aflatoxin albumin adducts as biomarkers for assessing aflatoxin exposure in Tanzanian children

PURPOSE

To determine levels of urinary aflatoxin M1 (AFM1) in children and correlate the concentrations with previously reported aflatoxin albumin adduct (AF-alb) levels in these children.

MATERIALS AND METHODS

Matched urine and blood samples were collected from 84 Tanzanian children aged 6-14 months old. From 31 children in one village (Kigwa), samples were collected at three time points six months apart. Samples were collected from 31 and 22 children from two different regions at the second time point only. Urinary AFM1 was measured using a commercial enzyme-linked immunosorbent assay (ELISA) kit with a modified protocol to improve sensitivity. AF-alb was measured using an established ELISA method.

RESULTS

The relative ranking of the three villages for exposure to aflatoxin based on either AFM₁ or AF-alb biomarker measurements was the same. In Kigwa village, both AFM1 and AF-alb levels were higher at six months post-harvest compared to baseline. However, at the next visit, the AFM1 levels dropped from a GM (interquartile range) of 71.0 (44.7, 112.6) at visit two to 49.3 (31.5, 77.3) pg/ml urine, whereas AF-alb levels increased from 47.3 (29.7, 75.2) to 52.7 (35.4, 78.3) pg/mg albumin between these two visits, reflecting the fact that AFM1 measures short-term exposure, whereas AF-alb measures longer term exposure. There was a correlation between AFB1 intake and AFM1 excretion (r= 0.442, p ≤ 0.001).

CONCLUSIONS

Urinary AFM1 is a good biomarker for AFB1 exposure in Tanzanian children, reflecting geographical and temporal variations in exposure to this foodborne toxin.