Polycyclic aromatic hydrocarbons (PAHs) are highly hydrophobic and organic lipophilic compounds with a fused ring structure comprising two or more aromatic rings (Domingo &Nadal 2015, Singh et al. 2016). The PAHs are mainly formed by the incomplete combustion or pyrolysis of organic materials and natural diagenesis, such as forest fires, fossil fuels and wood combustion, volcanic eruptions, industrial processes, and cooking (Singh et al. 2016, Sun et al. 2018). PAHs have received extensive attention as a persistent organic pollutant in the environment due to their high toxicity, carcinogenicity, teratogenicity, and mutagenicity to humans and animals. Previous studies demonstrated that several PAHs such as benzo(a)pyrene (BaP), chrysene (Chry), indeno[1,2,3-cd]pyrene (IP), and benzo(b)fluoranthene (BbF) had carcinogenic, mutagenic, genotoxic effects on animals (Rundle et al. 2000, USEPA 2014). In addition, the breast, lung, bladder, and skin cancers of humans are also related to exposure to PAHs (USEPA 2017). The PAH-DNA adducts formed by the carcinogen benzo(a)pyrene diol epoxide may increase the risk of lung cancer (Li et al. 2001). Different cooking methods (e.g., frying, smoking, roasting, and grilling) significantly affect the formation of PAHs in food (Ledesma et al. 2016, Li et al. 2015, Lin et al. 2011). Furthermore, it was also found that the concentrations of PAHs produced by cooking Chinese food were 29.5–130 ng m− 3, which was about twice that of cooking Japanese food and fast food (Li et al. 2003).
Food waste can be defined as the end products of various food processing industries, retailers, restaurants, and consumers (Lin et al. 2013). There has been a growing concern over the yield and treatment of food waste in both developed and developing countries (Grizzetti et al. 2013). Most food wastes are mainly disposed of in landfills or by incineration (Mo et al. 2017, Zhou et al. 2014). However, these traditional disposal methods have the disadvantages of occupying the land, producing greenhouse gases, and consuming social resources (USEPA 2018). The high organic content of food waste makes it a recyclable resource, and many studies have confirmed that fly maggots can efficiently biotransform food waste into animal feeds, fertilizer, and biodiesel (Wen et al. 2016). Niu et al. (2017) demonstrated that using housefly larvae to convert food waste can obtain value-added larvae protein (57.06 ± 2.19%), maggot oil (15.07 ± 2.03%), and organic fertilizers. Li et al. (2012) showed that the maximum yield of fatty acid methyl esters (FAME) obtained by feeding Chrysomya megacephala larvae (CML) with food waste was 87.7%, and its properties were within the specifications of the USA and European biodiesel fuel blend stock standards.
Chrysomya megacephala (CM) belongs to the Chrysomya genus (Calliphoridae family, order Diptera), which undergoes complete metamorphosis with four distinct stages (egg, larva or maggot, pupa, and adult) (Gabre et al. 2005). The CML is rich in proteins, essential amino acids, fat, vitamins, trace elements, and active substances such as lectin, lysozyme, antimicrobial peptide, and chitin (Badenhorst &Villet 2018, Huda et al. 2015, Li et al. 2012). The maggot grows fast and can consume a large amount of organic waste (e.g., livestock and poultry manure, and food waste) such that the material and energy in the organic waste can be transformed into insect nutrients (such as protein and fat) (Cickova et al. 2015). The maggot products after bioconversion can be used as animal feed protein, and the remaining residue can be reused as organic fertilizer (Li et al. 2012, Sing et al. 2014, Yang &Liu 2014)
Sing et al. (2014) reported that the CML as a protein source in fish feeds for culturing tilapia could improve the growth, feed efficiency, and survival of tilapia fry. However, the food waste (30–40%) and maggot products (25–32%) contain high lipid content (Li et al. 2012, Niu et al. 2017), which may lead to PAHs enrichment in feeds, which accumulate in poultry and aquatic products, and eventually reach humans. Therefore, it is necessary to ensure that aquatic products and poultry are raised by the feeds of larvae products that are relatively free of PAHs. The major objectives of this study were to investigate: (1) concentrations of PAHs in the CML fed with food waste; (2) the bioaccumulation of PAHs in Oujiang color common carp fed with the CML fish feed; and (3) to assess potential health risks based on PAHs concentration in the Oujiang color common carp.