Detectable levels of serum aflatoxin B1-albumin adducts in the United Kingdom population: implications for aflatoxin-B1 exposure in the United Kingdom.

ABSTRACT

This study aimed to estimate aflatoxin B1 (AFB1) exposure in the United Kingdom population by measuring levels of serum AFB1-albumin (alb), using immunoassay and high-performance liquid chromatography (HPLC) with fluorescence detection. A self-questionnaire on dietary habits from 104 volunteers (47 men and 57 women) in York was completed, and blood samples were collected. Serum alb was extracted, and AFB1-lysine (lys), the digest product of AFB1-alb, was isolated and measured. A sensitive ELISA (detection limit, approximately 1.4 pg of AFB1-lys) was developed. A good correlation was found between calibration of ELISA results and scintillation counting, for rats dosed with [3H]AFB1 (r = 0.972; P < 0.001). This ELISA was subsequently used to analyze human serum alb. For United Kingdom human sera, the mean adduct levels were 29.3 +/- 14.8 pg AFB1-lys equivalents (eq) mg albumin (males) and 26.9 +/- 14.4 pg AFB1-lys eq/mg alb (females). Confirmation of the ELISA data was sought using reversed-phase HPLC with fluorescence detection. HPLC chromatograms of digested York serum alb were compared to digested serum alb for humans from Qidong County, People's Republic of China, and from AFB1-dosed rats. These all gave similar HPLC profiles. Each sample contained fluorescent material that coeluted with and just before the AFB1-lys standard. Fluorescent fractions were found to be inhibitory in a separate anti-AFB1-lys ELISA, indicating that these earlier fluorescent peaks contained AFB1 residues. Our results suggest that measurable internal AFB1 exposure may be occurring in some United Kingdom individuals, albeit at lower levels than those seen for areas with high AFB1 exposure. The source of this exposure may reflect the known difficulties in accurately monitoring regulated imported foodstuffs and/or the lack of regulations on other potentially contaminated imports. However, no positive correlations were found between our AFB1-lys measurements and any dietary questionnaire information. Animal studies, as well as human studies, have been important in developing exposure and internal adduct relationships in humans. Based on this literature, our AFB1-alb data indicate a mean daily exposure of 3 microg of AFB1 and a mean internal dose in liver DNA of 5.9 adducts/10(7) nucleotides. We believe this may be an overestimate of the AFB1 exposure level in the United Kingdom, and further studies are needed to accurately relate external dose and internal AFB1 biomarkers in humans.