Andrew A. Meharg talks with
ScienceWatch.com and answers a few questions about
this month's Fast Moving Front in the field of Environment
& Ecology. The author has also sent along images
of their work.
Article: Variation in arsenic speciation and
concentration in paddy rice related to dietary
Authors: Williams, PN;Price, AH;Raab, A;Hossain,
Journal: ENVIRON SCI TECHNOL, 39 (15): 5531-5540 AUG 1
Addresses: Univ Aberdeen, Sch Biol Sci, Aberdeen AB24 3UU,
Univ Aberdeen, Sch Biol Sci, Aberdeen AB24 3UU,
Univ Aberdeen, Dept Chem, Aberdeen AB24 3UE, Scotland.
Why do you think your paper is highly
paddy in China.
It identified that inorganic arsenic, a non-threshold, class 1 carcinogen,
was elevated in rice grain from particular regions of the world, with that
elevation being due to anthropogenic sources.
Does it describe a new discovery, methodology, or
synthesis of knowledge?
It was the first paper to widely survey the inorganic arsenic content of
rice, and to establish what constituted background and elevated levels. It
also was the first to establish regions of the world at threat from high
inorganic arsenic in rice.
Would you summarize the significance of your paper
in layman’s terms?
The study identified rice, the dietary staple for half the world, as the
major route of the carcinogen inorganic arsenic into the human diet.
How did you become involved in this research and
were any particular problems encountered along the way?
I had a long history of studying the physiology of arsenic metabolism in
wild plants, but researching rice started when a Ph.D. student whom I was
supervising came from Bangladesh to study arsenic in rice, as he had
realized that problems may be occurring due to the practice of irrigating
rice with arsenic-contaminated tubewell water. Once we started to look into
arsenic in rice grain, we realized that this was a major problem with
respect to human dietary exposure from this carcinogen.
Where do you see your research leading in the
We have currently obtained major grant funding to breed rice with a lower
inorganic arsenic content, and, through this process, to identify the
genetics and physiology behind rice grain arsenic accumulation.
Do you foresee any social or political implications
for your research?
Yes, there are no food standards for inorganic arsenic in the USA and EU or
set by the World Health Organization. The EU, as a direct result of our
research, is currently reviewing this topic. In the UK, the government has
already issued warning advice that children under the age of 4.5 years
should not be fed rice milk.
Present research activity is very much focused on arsenic, and in
particular arsenic issues affecting SE Asia. The work on arsenic is both
the environmental chemistry and plant ecophysiology.
Environmental chemistry aspects of the work is interested in arsenic
sources and cycling within the environment, using state of the art
analytical approaches such as XAS and HPC-ICP-MS, HPLC-ES-MS-MS and laser
ablation-ICP-MS to study arsenic speciation in biotic and abiotic matrices
such as soils, sediments, minerals, plant & animal tissues. The work
concentrates on human and wild-life exposure to arsenic through
food-chains, and the microbial mechanisms regulating arsenic
transformations in the environment.
Plant ecophysiological aspects of the arsenic research investigates
mechanisms of arsenic uptake, internal transport and metabolism,
particularly how on how plants adapt to high levels of arsenic, the genetic
mechanisms behind adaptations, with the aim of breeding crop plants, such
as rice and wheat, for low grain arsenic.
Grain studies have been expanded to consider other toxic elements (cadmium
and lead) and well as essential trace micronutrients (copper, selenium
Professor Andrew A. Meharg
Fellow of the Royal Society of Edinburgh
Chair in Biogeochemistry
Institute of Biological & Environmental Sciences
University of Aberdeen Web