Raising a need for a risk assessment of bromoform transferred from feed to food
By Dr. Rozita
Spirovska Vaskoska (FoodLegal Scientist)
© Lawmedia Pty
Ltd, June 2021
The
risk of an adverse health effect from feed transferring a hazardous substance
into the food chain is one of the lessons learned from the disastrous
consequences for the UK beef industry that followed from the BSE outbreak. Thus,
assuring safe food also means assuring safe feed for animals.
In
recent years, Australian scientists have led international efforts to create animal
feed supplements that have the effect of reducing methane emissions from cattle
(both beef and dairy). Governments and corporations in Australia have invested
heavily in the commercial application of this technology. Bromoform is the
active substance in the formulation of the feed supplements sourced from
seawater algae.
While
the World Health Organization (WHO) has not done so, the U.S. Environmental
Protection Agency (US EPA) has assessed bromoform as a probable human
carcinogen based on evidence in animal studies.
Thus,
two important questions arise from the expanded commercial use of feed
supplements containing bromoform: 1) Is bromoform likely to end up in the food
chain?; 2) Could there be a carcinogenic risk in humans through consumption of milk
and meat if bromoform gets transferred from the supplemented feed to the milk
or meat?
The importance of reducing methane
emissions for the environment
The
food chain is considered to contribute to an estimated 8% (UK) - 31 % (EU) of
greenhouse emissions [1,2], with meat and dairy contributing half of these
emissions to an overall estimate of 18 % [2]. Methods of calculation of calculation
of emissions contributors vary, as do percentages calculated for different
countries. It has been estimated that methane (CH4) and nitrous
oxide (NO2) are the dominant emissions in the livestock industry in
the UK, followed by carbon dioxide (CO2). Methane comes from enteric
fermentation and manure management, while nitrous oxide comes from soils and
manures [3].
Using seaweed feed supplements to reduce
methane emissions
Several
groups of scientists, including leading Australian researchers, found that there
was scope for some seaweed-based feed additives to reduce methane production by
the animal by interfering with the process of methanogenesis. In particular,
these supplements are able to be derived from two types of seaweed being: Asparagopsis
taxiformis and Asparagopsis armata. The benefit of adding these
seaweed supplements to ruminant diet have been shown to include: the reduction
of methane production reaching over 80 % in in vivo studies and 99% in in
vitro studies [4]. Their methanogenesis reduction ability is due to the
active compounds, the most important being bromoform. Bromoform is stored in
gland cells of the seaweed. The mechanism of action of bromoform in methane
reduction is reacting with reduced vitamin B12 and inhibition of the B12
dependent methyl- transferase step of methanogenesis [5].
Is bromoform likely to end up in the
food chain?
To
date, there are five studies that have looked at the transfer and retention of
bromoform to milk and meat of cattle. Two of those studies did not detect
bromoform in meat despite the high intake [4,6]. Two studies found similar
levels in the milk of the control and the fed animals [7,8]. One study found
bromoform transfer in the milk [9]. However, the levels were inconsistent: they
found positive samples at 3 of the 18 tested time/level points and not in all
cows [9].
Metabolic and toxicological studies for
bromoform
Bromoform
has been found in a case of an accidental human intoxication in the liver,
kidney, brain, lungs and stomach/ intestines [10]. Animal studies have also
shown its immediate presence in the blood and adipose tissue, but also showed
bromoform has a quick metabolism, particularly in the liver [10]. Animal
studies have shown excretion though the urine and lungs [10].
Bromoform
belongs to a group of compounds known as halogens, which include bromoform and
chloroform. Halogens have elements with large negative electron affinity that
combine with other compounds to reach stability. The chemical similarity of
bromoform to chloroform, which is a known carcinogen, has triggered scientific
assessments of bromoform for its safety.
Animal
studies of its safety have shown that bromoform can enlarge tumours in the
large intestine and cause some developmental toxicity [10]. Results on
genotoxicity of bromoform have been inconsistent [10].
Classification
and guideline levels for bromoform globally and in Australia
Different evaluating bodies have
approached classification of bromoform differently. Guideline levels have been
established for bromoform or their chemical group (trihalomethanes) in
Australia and globally in relation to drinking water.
International
The
International Agency for Research on Cancer has placed bromoform in group 3,
which means not classifiable as to its carcinogenicity to humans.
The
World Health Organization (WHO) has set up a guideline value of 100 µg/L (0.1
mg/L) of bromoform as a disinfection by-product in drinking water [11].
The
Tolerable Daily Intake (TDI) for bromoform has been set up at 17.9 µg/kg body
weight and has been explained by the WHO as “based on the absence of
histopathological lesions in the liver in a well-conducted and well documented
90-day study in rats, using an uncertainty factor of 1000 (100 for intraspecies
and interspecies variation and 10 for possible carcinogenicity and short
duration of exposure)”.
Australia
The
Australian Drinking Water Guidelines establish a level of 250 µg/L (0.25 mg/L)
for all trihalomethanes together and does not set up a specific guideline level
for bromoform. The explanation is that these compounds are metabolized
similarly in the human body [12]. The newest Australian guidelines (updated this
year - 2021) mention the need to aim for a lower level of trihalomethanes,
but also mention the valuable need of water disinfection by chlorine which
prevents other safety risks [12].
USA
By
contrast to the WHO, the U.S. Environmental Protection Agency (US EPA) has
categorized bromoform as a B2 Probable human carcinogen based on
sufficient evidence of carcinogenicity in animals. The US EPA has set up the
following guideline levels [14]:
- Non
cancer Reference Dose for Oral Exposure (RfD) 20 µg/kg- day (0.02 mg/kg-
day) for hepatic lesions
In the USA, the Centre for Disease Control and Prevention (CDC) has stated that bromoform is not found in food [13].
However,
whilst this might have been the case in the CDC study, this might no longer be
the case if it has been shown that bromoform is able to be transferred to food
through feed.
The importance of instigating regulatory assessment and monitoring immediately
In Australia there are two licensed producers of seaweed feed supplements for methane reduction, and the products are patented. Expansion in seaweed commercialization will accelerate a greater uptake by farmers seeking to improve sustainable cattle feeding practices. At the same time there are global initiatives in relation to ensuring the safety of seaweed products. In early 2021, a Safe Seaweed Coalition [14] was established at an international level to address consumer safety in relation to seaweed usage.
One of the recent studies that did not find any retention in meat nevertheless raised the need for close monitoring of the situation with the following statement: "Due diligence requires continued monitoring if inclusion periods are extended and the cumulative intake levels are increased which may be the case in some dairy systems“[6].
Clearly, if exposure to bromoform is likely to increase, it is important for Australian regulators to assess safety and to set regulatory levels regulatory levels for exposure in foods and that ongoing monitoring be mandatory.
References
1. Gibbons, J.M., S.J. Ramsden, and A. Blake, Modelling uncertainty in greenhouse gas emissions from UK agriculture
at the farm level. Agriculture, Ecosystems & Environment, 2006. 112(4): p. 347-355.
2. Garnett, T., Livestock-related
greenhouse gas emissions: impacts and options for policy makers.
Environmental Science & Policy, 2009. 12(4):
p. 491-503.
3.
Morgavi, D., et al., Microbial ecosystem and methanogenesis in
ruminants. animal, 2010. 4(7):
p. 1024-1036.
4.
Roque,
B.M., et al., Red seaweed (Asparagopsis
taxiformis) supplementation reduces enteric methane by over 80 percent in beef
steers. Plos One, 2021. 16(3):
p. e0247820.
5.
Honan, M., et al., Feed additives as a strategic approach to
reduce enteric methane production in cattle: Modes of action, effectiveness and
safety. Animal Production Science, 2021.
6.
Kinley, R.D., et al., Mitigating the carbon footprint and
improving productivity of ruminant livestock agriculture using a red seaweed.
Journal of Cleaner Production, 2020. 259:
p. 120836.
7. Roque, B.M., et al., Inclusion
of Asparagopsis armata in lactating dairy cows’ diet reduces enteric methane
emission by over 50 percent. Journal of Cleaner Production, 2019. 234: p. 132-138.
8. Stefenoni, H., et al., Effects
of the macroalga Asparagopsis taxiformis and oregano leaves on methane
emission, rumen fermentation, and lactational performance of dairy cows.
Journal of Dairy Science, 2021. 104(4):
p. 4157-4173.
9. Muizelaar, W., et al., Safety
and transfer study: Transfer of bromoform present in asparagopsis taxiformis to
milk and urine of lactating dairy cows. Foods, 2021. 10(3): p. 584.
10. 12. RAIS. Formal toxicity summary for bromoform.
1995; Available from: https://rais.ornl.gov/tox/profiles/bromofrm.html.
11. WHO, Guidelines for
drinking-water quality. 2017.
12. NHMRC. Australian Drinking
Water Guidelines (2011)- Updated Marhc 2021. 2021; Available from: https://www.nhmrc.gov.au/about-us/publications/australian-drinking-water-guidelines#block-views-block-file-attachments-content-block-1.
13. CDC, Public health statement
for bromoform and dibromochloromethane. 2015.
14. Coalition, S.S.; Available from: https://www.safeseaweedcoalition.org/.
This is general information rather than legal advice and is current as of 2 Dec 2021. We recommend you seek legal advice for your specific circumstances before making any commercial decisions.