Exposure assessment to mycotoxins in workplaces: aflatoxins and ochratoxin A occurrence in airborne dusts and human sera

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Abstract

In order to evaluate the possible presence of mycotoxins in airborne particulates, a micro-method by HPLC was performed for aflatoxins and ochratoxin A (OA) in dust samples. A total of 44 samples of airborne particulates were collected in three different workplaces in Tuscany (central Italy), where three of the most susceptible foodstuffs (cocoa, coffee and spices) are processed. Air samples were obtained through both area and personal samplings collected during the entire workshift. Whenever possible, workers’ sera were collected in order to check the biomarker of exposure for OA. Dust samples were contaminated at different levels, ranging from less than the limit of detection to 0.080 ng for aflatoxins and to 5.481 ng for OA. The wide range of toxin levels could be related to different causes, such as the distance between the worker and the stocked raw materials, the worker's job, the exposure time and the amount of particulate matter sampled. Airborne levels of OA, and aflatoxins B1, B2, G1 and G2 were in the range 0.001–8.304, <0.002–0.038, <0.002–0.029, <0.002–0.036 and <0.014–0.131 ng/m3, respectively. OA levels in workers’ sera showed much higher results (0.94–3.28 ng OA/ml) than the mean level found in the Italian population, showing that inhalation in the workplace can be considered a route of exposure additional to the consumption of contaminated foodstuffs.

Introduction

Microscopic filamentous fungi can develop on a wide variety of food commodities and, under suitable environmental conditions, can lead to the production of highly toxic chemical substances, commonly known as mycotoxins. The most widespread and studied mycotoxins are metabolites of some genera of moulds such as Aspergillus, Penicillium and Fusarium. Quite peculiar conditions may influence mycotoxin biosynthesis, such as climate, geographical location of crops, cultivation practices, storage and type of substrate. Valuable reviews on mycotoxin biosynthesis have been published by Krog [1] and by Smith et al. [2]. Mycotoxin levels are generally not affected by technological food processing, and as far as grains are concerned, the toxins can residue both on the outer surface and in the inner portions of the kernels.

Toxicity has been extensively investigated for the most important mycotoxins, such as aflatoxins, ochratoxin A (OA) and Fusarium toxins, and much information derived from toxicokinetics in animal models has also been obtained. The adverse effects are mainly related to genotoxicity, carcinogenicity, mutagenicity, teratogenicity and immunotoxicity. Mycotoxins are able to form adducts with various molecular receptors, such as DNA, RNA, functional proteins, enzymatic co-factors and membrane constituents.

In particular, aflatoxin B1 (AFB1) has been shown to be genotoxic and one of the most powerful hepatocarcinogens. Currently, according to the International Agency for Research on Cancer (IARC), this toxin has been classified in group 1A (adequate evidence for carcinogenicity for humans) [3]. OA is a nephrotoxin, for which correlations have been observed between its levels in food/sera and Balkan endemic nephropathy (BEN)/urinary tract tumours (UTT). A review on the toxicity of mycotoxins was published by Richard [4].

Mycotoxin exposure mainly occurs via the food chain, the most risky commodities being cereals, oleaginous seeds, cocoa, coffee, grapevine, wine, fruits, spices and dried fruit.

Inhalation of contaminated airborne aerosols can represent an additional route of exposure, which, however, has not yet been exhaustively investigated. In fact, mycotoxins can be found in airborne particulates of environments where some susceptible commodities are treated, such as warehouses, harbours and laboratories. Moreover, the presence of mycotoxins in domestic households, as a consequence of inappropriate hygiene conditions, has been demonstrated [5]. Experimental evidence has shown that in humans the inhalation of fungal spores can cause asthma and rhinitis, while mycotoxin-contaminated dusts have been proved to have immunosuppressive effects [6] due to the inhibition of phagocytosis and of alveolar macrophage functions. Furthermore, epidemiological studies revealed a high frequency of liver, lung and biliar tract tumours in workers handling mycotoxin-contaminated food commodities [7].

In a previous paper, we assessed aflatoxin and OA exposure in Italy through evaluation of their occurrence in food and, as far as OA is concerned, through toxin levels in biological fluids (blood and milk), both in the general population and in some at-risk groups of consumers [8], [9]. The output of a study dealing with external and internal doses of subjects occupationally exposed to OA has also been submitted for publication [10].

In the present paper, exposure assessment of the aflatoxins B1, B2, G1 and G2, and OA via inhalation in selected workplaces is described. Within this scope, an analytical micro-method for the determination of aflatoxins and OA was carried out and is described. Levels of the airborne toxins in selected workplaces are also given. In order to link, whenever possible, the assessment of the toxins in the airborne particulates with biomarkers in serum, the results were matched with the previously reported evaluation of OA level in sera samples of workers exposed to contaminated dusts [10].

Section snippets

Sampling of airborne particulates

Airborne particulates were collected either by area or by personal sampling. Air was drawn through 25-mm glass fibre filters without binders (0.8-μm pore size, 25-mm diameter; Gelman Science, Michigan, USA, code 66075) by means of Aircheck pumps (SKC, USA) at a flow rate of 2.0 l/min. For evaluation of the inhalable fraction of the airborne particulates, the filters were supported by IOM holders according to ISO 7708 [11].

In most cases sampling was performed during the entire workshift, even

Serum samples

According to Italian legislation, the aim of the study was communicated beforehand to the donors. A total of 26 workers equipped with personal samplers were asked for their agreement to the withdrawal of serum. Six out of the workers tested (n=26) workers provided their consent. The withdrawal of blood samples was carried out at the end of the work-shift.

Occupational environments

The occupational environments were chosen on the basis of the commodities more susceptible to mycotoxin contamination. Green coffee, some spices and cocoa beans are usually imported from countries where the environmental and hygiene conditions are favourable for the development of moulds, and aflatoxins and OA are frequently reported as contaminants of these raw materials. However, it should be underlined that the risk attributable to the ingestion of these particular food commodities is

Conclusions

The analytical method developed for measuring occupational exposure by environmental and biological monitoring gave precise and accurate results, and it must be considered adequate for risk assessment of aflatoxins B1, B2, G1 and G2, and of OA airborne in the workplace. The sensitivity of the method has also been shown to be very good, even at very low environmental levels of the toxins. Since a number of foods and animal feeds can be contaminated by aflatoxins and OA in many workplaces,

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