industry and environment - DTIE

Chemicals management
The evolution of Canada’s approach to
minimizing environmental and health risks
from mercury
Wanda M. A. Hoskin, Senior International Advisor, Minerals and Metals Sector, Natural Resources Canada, 580 Booth Street,
Ottawa, Ontario K1A 0E4, Canada (whoskin@nrcan.gc.ca)
Summary
Human health concerns underlie Canada’s approach to limiting releases of anthropogenic
mercury. Mercury is a naturally occurring element that is ubiquitous in the environment. Routes
of exposure are complex. While the scientific literature and policies and regulations refer to
mercury levels in the environment, it is methylmercury (a neurotoxin) that is referred to. Methylation
of particulate and reactive mercury into organic methylmercury produces toxic effects.
The Canadian government has promulgated a range of policies and regulations to minimize
health and environmental risks from this and other toxic chemicals. It also works with Canada’s
provincial and territorial governments and is active in bilateral, regional and international
activities.
Résumé
Des préoccupations concernant la santé des hommes sous-tendent l’approche adoptée par le
Canada pour limiter les rejets de mercure anthropiques. Le mercure est un élément naturel
omniprésent dans l’environnement. Les voies d’exposition sont complexes. Bien que la documentation
scientifique, les politiques et les réglementations parlent de niveaux de mercure
dans l’environnement, c’est au méthylmercure (une neurotoxine) qu’elles font référence. La
méthylation du mercure particulaire et du mercure réactif produit le méthylmercure organique,
fortement toxique. Le gouvernement canadien a adopté une série de politiques et de réglementations
pour réduire les risques que présentent ce produit chimique et plusieurs autres pour
la santé publique et l’environnement. Il travaille également avec les autorités provinciales et territoriales
du pays et participe activement à des activités bilatérales, régionales et internationales.
Resumen
El enfoque canadiense para limitar la liberación de mercurio antropogénico es resultado de
una preocupación por la salud humana. El mercurio es un elemento natural ubicuo en el medio
ambiente y las vías de exposición humana al mercurio son complejas. Aunque la literatura
científica, las políticas y la normatividad hacen referencia a los niveles de mercurio en el ambiente,
en realidad se refieren al metilmercurio (una neurotoxina). El proceso de metilado de
partículas de mercurio y de mercurio reactivo para producir metilmercurio orgánico tiene efectos
tóxicos. El gobierno canadiense ha promulgado una serie de políticas públicas y normativas
a fin de minimizar los riesgos ambientales y para la salud que entrañan éste y otros
productos químicos tóxicos. Asimismo, colabora con los gobiernos provinciales y territoriales del
país, y participa en actividades bilaterales, regionales e internacionales.
Mercury is found in air, water, soil and
biota (the flora and fauna of a region). It
exists in many forms in the environment.
These forms have different properties that
affect distribution, uptake in the food chain (i.e.
bioavailability) and toxicity.
Mercury is a naturally occurring element, persistent
by definition. It is unique among metals,
in that it is liquid at ambient temperature. Named
after the Roman god of commerce, travel and
thievery, it has been used for more than 3000
years. Also known as “quicksilver”, it was known
to the ancient Chinese and Hindus before 2000
BC. Mercury has been found in tubes in Egyptian
tombs dating from about 1500 BC. It was first
mentioned by Aristotle in the fourth century BC,
when the heavy, silvery-white metal was used to
form amalgams with other metals for ointments
and cosmetics. Elemental mercury is readily transformed
into mercury vapour. The vapour can be
transported by air and is readily taken up by airbreathing
organisms.
Reactive mercury (referring to the ionic form)
can easily be converted into methylmercury, an
organic compound that is highly toxic.
Methylmercury is bioavailable, bioaccumulates,
and biomagnifies as it moves up the food chain
from fish to mammals, including humans.
Particulate mercury consists of compounds that
are bound in soil, sediment and aerosol particles.
These compounds are not generally easily
bioavailable, but they can be released as a result of
human activity. For example, flooding of large
areas of land for hydroelectric generating stations
generally transforms particulate mercury into
methylmercury, potentially contaminating fish
and fish-eating mammals in the area.
Redistribution of mercury as a result of human
activity or industrial processes (anthropogenic
sources) has increased since the industrial era. It
could now be responsible for a significant percentage
of total emissions to the atmosphere each
year. The main sources of mercury emissions
today are coal-fired electric power plants, waste
incinerators, chlor-alkali facilities still using the
mercury cell process, 1 primary copper and lead
smelters, and cement manufacturing. Mercury is
still used in batteries, but this use has been declining
as manufacturers switch to alternative metals.
Other shrinking markets include electrical applications
(ranging from metallic mercury switches
in thermostats to mercury-vapour discharge
lamps), dental amalgams, temperature- and pressure-measuring
devices, detonators, pigments and
pharmaceuticals. While increased concerns related
to the health and environmental risks of mercury
exposure have led to greater restrictions on
its uses, its unique properties will likely guarantee
its use in some key sectors (e.g. energy-efficient
fluorescent lamps) in the foreseeable future.
Environmental and health issues,
monitoring and assessment
Methylmercury is a known neurotoxin that slows
fœtal and child development. It causes irreversible
deficits in brain function. Scientific debate to
more precisely determine the level at which effects
begin to occur is ongoing, although recent epidemiological
studies on Arctic populations have
shown that even low levels of methylmercury have
some effect (even if much more subtle), affecting
fine motor function, visual spatial abilities and
verbal memory. 2
It is important to point out that while the scientific
literature, policies and regulations refer to “mercury”
levels in the environment, it is methylmercury
that is referred to and it is the methylation of particulate
and reactive mercury into organic methylmercury
that produces toxic effects.
Effects on biota and the establishment of mercury
concentration trends in the environment are
UNEP Industry and Environment April – September 2004 ◆ 39