Dr. Harding has numerous publications in
scientific journals and peer-reviewed conference proceedings on
toxicology and environmental contaminants.
For more
information, see the
Contaminated Sites, Pulp Mill and Mining pages.
Example of a Toxicology Project
From
2001 through 2007, SciWrite investigated the effects of
selenium on waterbirds in the Rocky Mountains of southeast British
Columbia. In 2010, SciWrite assessed uptake of selenium along the
Wolverine River, northeastern B.C.
Selenium
is a highly embryotoxic element that can reach high concentrations
in agricultural and coal mine drainage water. In 2001–2002, SciWrite
assembled and led a team of biologists and technicians to collect
eggs of two bird species (sandpipers and dippers) that live along
fast-flowing streams and relate the selenium concentration to
measures of productivity: egg health, number of eggs hatched,
nestling health, and number of young fledged. The client, a
consortium of coal mines, asked SciWrite to publish the results in
the scientific literature:
Harding, L.E., M. Graham, and D. Paton. 2005. Accumulation of
selenium and lack of effects on productivity of American dippers (Cinclus
mexicanus) and spotted sandpipers (Actitis macularia) in
lotic streams. Archives of Environmental Contamination and
Toxicology 48(3):414-423
In
2003–2004, SciWrite extended the study to ducks and geese nesting in
marshes (as opposed to flowing streams) where selenium uptake was
likely to be greater. SciWrite's team collected, measured, and
examined the embryos of eggs and analysed the eggs for selenium in
contaminated and control marshes. We then assessed hatchingsuccess
by counting broods.
In 2003–2006
SciWrite completed a third study of selenium uptake and effects in
red-winged blackbirds. The encompassed biology, toxicology,
immunology, pathology, biochemical analysis for selenium biomarkers,
and chemical analysis. It required the participation of five
laboratories (three with different specialties in chemical analysis,
one for wildlife veterinary pathology, and one for biomarker
assays). We collected an egg from each nest, examined and measured
the embryo, and submitted the contents for chemical analysis. We
examined nestlings for signs of selenium-related abnormalities and
followed each nest through to successful fledging. From each of six
study sites (three contaminated and three controls) we drew blood
from nestlings to measure glutathione peroxidase activity, a
biochemical indicator of selenium exposure. A subset of these was
sacrificed to compare blood glutathione peroxidase with liver
selenium, and to compare pathologies of birds that died in the nest
with those that were sacrificed while healthy. From each study site,
we collect insect prey items from nestlings' stomachs to assess
selenium in their diets. This study resulted in two significant
discoveries: a hormesis relationship of selenium with productivity,
and a non-linear selenium uptake curve in blackbirds. In 2007, the
client asked Dr. Harding to publish the results; the paper was
published in Science of the Total Environment; Dr. Harding
later published a paper on red-winged blackbird breeding biology in
British Columbia Birds.
Harding, L. E. Non-linear Uptake and Hormesis Effects of
Selenium in Red-winged Blackbirds (Agelaius phoeniceus).
Science of the Total Environment
389:
350-366.
Harding, L.E. 2010. Breeding
Biology of Red-winged Blackbirds in the Rocky Mountains. British
Columbia Birds 20:16–23
In 2010 and 2011, SciWrite completed similar
studies of selenium uptake in spotted sandpipers and red-winged
blackbirds at a mine site near Tumbler Ridge, North-eastern British
Columbia.
