Potential dietary exposure to bromoform from its use as a methane inhibitor

The red seaweeds, Asparagopsis taxiformis and A. armata are effective at inhibiting methane production in ruminants, mediated by the bioactive, bromoform. Bromoform from non-seaweed sources is also being formulated as a methane inhibitor. Bromoform is a trihalomethane in the same family as chloroform, dibromochloromethane, and bromodi-chloromethane, all common drinking water disinfection by-products. This study used recent research findings about levels of bromoform residues in processed milk products combined with dietary patterns in New Zealand and overseas, to estimate potential dietary exposure to bromoform following use of bromoform as a methane inhibitor in dairy cows. The estimates of dietary bromoform exposure (mean and high) for New Zealanders conformed to an expected pattern, with dietary exposure, expressed on a body weight basis, generally decreasing with increasing age of the consumer. Mean estimates of dietary exposure, across age groups were in the range 9.2-40 ng/kg bw per day, while high (95th percentile) estimates were in the range 22-100 ng/kg bw per day. Cheese and liquid milk were the major contributors to dietary bromoform exposure. Non-cancer and cancer risk estimates for the New Zealand population, based on the derived dietary exposure estimates indicate negligible risks from the potential presence of bromoform in dairy products.