Mutagenic and oestrogenic activities of commercially processed food items and water samples : a comparison between Finland and Nigeria

Commercially processed food, drinking-water sources and effluent waters discharged into bodies of water from wastewater treatment plants are putative but yet poorly delineated sources of human exposure to chemical mutagens and oestrogen-like chemicals globally. To this end, this study was aimed at determining the current situation for a possible comparison between a European country (Finland) and an African country (Nigeria). A total of 116 commercially processed food items and ready-to-eat snacks (three lots each) were obtained from Finland (60) and Nigeria (36) for initial screening, as well as sachet-pure water (16 different brands) from Nigeria, bottled still and mineral waters (10 brands each), tap water (hot and cold collected over a 3-month period) and influent and effluent water samples from both a drinking-water treatment plant (collected over a 3-month period) and a wastewater treatment plant (collected over a 2-year period) in Finland. All samples were collected in their respective countries and extracted by established methods. The mutagenic potential of the food extracts was first determined by the standard plate incorporation assay (Ames test), using two strains of Salmonella enterica sv. Typhimurium (TA 100 and TA 98) in the presence and absence of metabolic activation (S9 mix), and subsequently by a methylcellulose overlay, as well as treat-and-wash assays, while the oestrogenicity of the water and food samples, as well as food packaging materials, was determined by a yeast bioluminescent assay, using two recombinant yeast strains (Saccharomyces cerevisiae BMAEREluc/ERα and S. cerevisiae BMA64/luc). The cytotoxicity of the food extracts was measured by the trypan blue and lactate dehydrogenase tests, using the HepG2 cell line, as well as by the boar sperm motility assay, while possible DNA damage was assessed by the comet assay. The mutagenicity of commercially processed food items in Finland was generally low: 60% or 73% were non-mutagenic in S. Typhimurium strains TA 100 and TA 98, respectively. While the majority of the initially positive samples proved negative in the complementary assays, cold cuts of cold-smoked beef, grilled turkey and smoked chicken (a single batch of each) were also mutagenic in all three assays with the TA 100 strain, with and without metabolic activation, indicating that the mutagenic effect was not secondary to histidine release from the food products. The low mutagenicity outcome of the Finnish food items was further confirmed by independent chemical analyses of similar food products for four polycyclic aromatic hydrocarbons. In contrast to the outcome in Finland, the majority of food items from Nigeria (75%) were mutagenic in the Ames test, either in the presence or absence of the S9 mix and in either of the strains. Chin-chin, hamburger, suya and bean cake were mutagenic in all three assays with the Salmonella TA 100 strain, either in the presence or absence of the S9 mix. However, none of the food samples caused DNA damage in the comet assay. They were also not cytotoxic in any of the three assays measuring this aspect. In all, 31% of the sachet-packed water samples in Nigeria were oestrogenic, with concentrations ranging from 0.79 to 44.0 ng/l oestradiol equivalent concentrations (EEQs), while the tap and bottled water samples from Finland showed no signs of oestrogenicity in the in vitro test. Similarly, the oestrogenic activity of the influent samples from the wastewater treatment plant in Helsinki were generally low (from below the limit of detection to 0.7 ng/l EEQ), except in March and August 2011, when relatively high levels (14.0 and 7.8 ng/l EEQ, respectively) were obtained. No oestrogenic activity was recorded in any of the treated effluent samples from the wastewater treatment plant, nor was any in the influent and effluent samples from the drinking-water plant. The outcome of this study implies that Nigerian food items and drinking-water sources are more likely to contain mutagenic and oestrogenic chemicals than their Finnish counterparts, and efforts should be made to reduce the level of human exposure to these chemicals in the diet.

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