Campaigning for safer, healthier food for all - The Food Commission

food safety
Climate change: the
risk of food poisoning
Among the many problems
that climate change may bring
to the British Isles is a rise in
the risk of food poisoning,
especially during the winter
months. Tim Lobstein reports
With alarming regularity, the media tells
us of the likely rise in temperatures
we will face over the coming century
if action is not taken to curb greenhouse gas
emissions. In April, the government’s Chief
Scientific Officer Sir David King projected a likely
rise in global temperature of at least 3°C. But
what effect will this have on food safety?
Prevailing climate has a significant effect on
the risk of getting food poisoning. Currently, the
number of food poisoning cases increases in
summer and decreases in winter, and there is a
correlation between prevailing temperatures and
reported food poisoning incidence.
A 1995 study by Bentham and Langford
showed that above a threshold of around 7.5°C
the rate of food poisoning rises strongly with the
prevailing temperature (see ref 1 in box, right).
On this basis the authors estimated food
poisoning incidence if global temperatures were
to rise. On the basis of a 2°C rise, the figures
suggest that food poisoning incidence could
increase by as much as 20%.
In the UK the highest increase in incidence
may occur for the period from autumn though to
spring, when global warming will increasingly
raise the prevailing temperature above the 7.5°C
threshold (this is illustrated in the graph, based
on prevailing temperatures in East Kilbride,
Scotland). If temperatures rise by 4°C then the
figures for winter months leap again.
A contributing factor may be an increase in
the fly and blowfly populations, which typically
breed at temperatures above 10°C. Larvae can
develop at temperatures as low as 3.5°C. The
result of milder winters could mean greater
problems of food contamination with insectmediated
enterobacteria and enteroviruses.
Day-night temperature changes may also be
important. Milder night-time temperatures can
increase the proliferation of micro-organisms in
food left in ambient temperature, and increase
the numbers of insects that transmit disease.
Warming seas may mean that some
biotoxins associated with warmer weathers,
such as the fish-borne toxin that causes
Ciguatera sickness, may extend their range to
higher latitudes, raising the risk of poisoning for
people eating fish and shellfish.
There may also be an increase in the
occurrence of toxic algal blooms which have
complex relationships with human poisoning and
are ecologically and economically damaging.
Increased humidity can encourage fungal
growth, raising the risk of fungal-based contamination
of food (e.g. with ochratoxin and aflatoxin).
Further, periods of drought encourage mice and
rats to seek sources of food in human houses,
which raises the risk of spreading rodent-borne
diseases, as well as affecting food security.
Sir David King warned that 10% of the world's
population face famine as climate change threatens
agricultural production. But we must also
face up to the fact that what food is available will
increasingly be at risk of contamination.
Number of days each month in which mean daily temperature rises above 7.5°C
Temperature data for East Kilbride, Lanarkshire, 1995 (adapted from UK Meteorological Office, 2001)
in the food chain
does food poisoning occur?
The correlation between prevailing
temperatures and reported food poisoning
incidence is often interpreted as being a
problem caused by neglectful consumers.
Local authorities and national agencies
put out leaflets and advertising telling us all
to be sure to keep chilled food in the fridge,
to throw away out-of-date products, and to
wash our hands. Messages are also sent to
caterers reminding them of the need to
monitor their food storage and food
preparation activities, and to refresh their
hygiene training.
However, Bentham and Langford's
research found that the incidence of food
poisoning was most strongly associated
with the temperature prevailing during the
month prior to the month when the food
poisoning outbreak occurred. 1 Temperatures
in the earlier month accounted for more of
the variation in food poisoning incidence
and implied that conditions earlier in the
food production process posed a more
significant food poisoning risk than those
just prior to consumption.
The authors suggest that attention
should be paid to problems occurring early
in the food chain, such as the condition of
animals prior to slaughter and the likelihood
that they may be harbouring infection. Such
infection may be associated with
contaminated feedstocks, water or other
inputs. Contamination levels may be higher,
or the disease spread more rapidly through
herds and flocks, during warmer months.
Bacteria may also survive for longer in
warmer conditions through the transport,
slaughter and cutting processes. The
authors therefore suggest that
slaughterhouse procedures should also be
improved, a finding echoed in several
investigations into the causes of recent food
poisoning outbreaks. 2,3
1. Bentham G and Langford A H, Climate change
and the incidence of food poisoning in
England and Wales, Int J Biometeorol, 39, 81-
86, 1995.
2. House of Commons, Salmonella in eggs: First
report, House of Commons Agriculture
Committee, February and December, HMSO,
London 1989.
3. Pennington H, Report on the circumstances
leading to the 1996 outbreak of infection
with E.coli 0157 in Central Scotland, the
implications for food safety and the lessons
to be learned, The Scottish Office,
Edinburgh, 1997.
Food Magazine 73 6
Apr/Jun 2006
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