Following a request from the European Commission, the Panel on Food Additives and Nutrient Sources added to Food (ANS) of the European Food Safety Authority (EFSA) was asked to deliver a scientific opinion on the re-evaluation of butylated hydroxyanisole (BHA) (E 320) as a food additive.
BHA (E 320) is a synthetic antioxidant authorised as a food additive in the EU that was previously evaluated by the Joint FAO/WHO Expert Committee on Food Additives (JECFA) several times, the latest in 1989 and the EU Scientific Committee for Food (SCF) in 1989. Both committees established an ADI of 0.5 mg/kg bw/day with the ADI of the SCF being a temporary ADI. Both ADIs were based on proliferative changes in the rat forestomach.
BHA is a mixture of two isomers with full chemical names 2-tert-butyl-4-hydroxyanisole and 3-tert-butyl-4-hydroxyanisole. Specifications have been defined in the EU legislation in Directive 2008/128/EC and by JECFA. The purity is specified to be not less than 98.5% of C11H16O2 and not less than 85% of the 3-tertiary-butyl-4-hydroxyanisole isomer.
In general, BHA is rapidly absorbed from the gastrointestinal (GI) tract, metabolised and excreted in the form of metabolites mainly in urine and/or faeces. The major metabolites of BHA are the glucuronides, sulphates and free phenols, including tert-butylhydroquinone (TBHQ). The proportions of the different metabolites vary in different species and also for different dose levels. The acute toxicity of BHA is low, with an LD50 in mouse and rat > 2000 mg/kg bw/day.
In general, the majority of the genotoxicity studies indicate a lack of potential for BHA to induce point mutations or to interact with or damage DNA. BHA and its metabolite TBHQ have been reported to induce chromosomal aberrations in vitro in the presence of metabolic activation. The Panel recognised that the clastogenic activity exerted in vitro by BHA and TBHQ is likely to be secondary to the formation of reactive oxygen species via pro-oxidant chemistry, and that such a mechanism of genotoxicity is considered thresholded.
A large number of long-term toxicity and carcinogenicity studies have been performed with BHA, demonstrating proliferative changes in the forestomach. The studies have included species with a forestomach (rats, mice, hamsters) and without (guinea-pigs, dogs). The Panel noted that gastric epithelial hyperplasias, papillomas and carcinomas were only seen in species with a forestomach.
The Panel concluded that the long term studies in rats reveal the lower confidence limit of the benchmark dose (BMDL10) values for forestomach hyperplasia of respectively 115 mg/kg bw/day and 83 mg/kg bw/day. Forestomach hyperplasia was the critical effect on which SCF and JECFA based their acceptable daily intake (ADI).
The Panel noted that a new reproductive and developmental toxicity study had been published since the latest SCF and JECFA evaluations. The Panel noted that the study was not performed according to OECD guidelines and that several of the endpoints studied are not part of regular OECD guidelines for testing reproductive and developmental toxicity. The Panel also noted that the decreases reported in the parameters that were stated to be affected were generally less than 10% without a clear dose response, and that the ranges reported for these parameters overlap due to large standard deviations. Thus the Panel concluded that the effects reported in this study that were statistically significant (at p<0.05) were not biologically relevant.
The Panel also noted that other studies gave a no-observed-adverse-effect level (NOAEL) for reproductive and developmental toxicity of 0.125% BHA in the diet (equivalent to a dose of at least 100 mg/kg bw/day) in rats, and a NOAEL for reproductive and teratogenic parameters of 400 mg/kg bw/day in rabbits. The NOAEL in rats defined in the study of Vorhees et al. in 1981 was based on pups showing growth retardation, increased mortality and behavioural effects at higher dose levels.
The Panel noted that forestomach hyperplasia in rats was the critical effect on which SCF and JECFA based their ADI. The Panel considered that humans do not have a forestomach and that forestomach hyperplasia in rodents may no longer be considered relevant for human risk assessment.
Overall, the Panel concluded that the present database does give reason to revise the ADI of 0.5 mg/kg bw/day.
The Panel noted the potential endocrine effect of BHA which has been investigated in a number of studies. The Panel also noted that studies on reproductive and developmental toxicity in rats gave a NOAEL of 0.125% BHA in the diet (equivalent to a dose of at least 100 mg/kg bw/day). This NOAEL was based on pups showing growth retardation, increased mortality and behavioural effects at higher dose levels. Based on a NOAEL of 100 mg/kg bw/day and using an uncertainty factor of 100 the Panel established an ADI of 1.0 mg/kg bw/day. Since the NOAEL of 100 mg/kg bw/day is in the range of the BMDL10 values for forestomach hyperplasia in rats of respectively 115 mg/kg bw/day and 83 mg/kg bw/day the Panel concluded that this NOAEL also covers the BMDL10 values for forestomach hyperplasia observed in the rat. This NOAEL was also below the dose of 500 mg/kg bw/day causing oesophageal basal cell proliferation in monkeys.
Exposure estimates to BHA at Tier 2 for children and the adult population at both the average and high level exposures are unlikely to exceed the ADI of 1.0 mg/kg bw/day.
The Panel noted that the JECFA specification for lead is < 2 mg/kg whereas the EC specification is < 10 mg/kg.