Table 2 - Potential health effects of ingesting
metals in drinking water.
For centuries the solitary goal for
urban drainage was to move
excess water to prevent
flooding with an “out of sight,
out of mind” mentality. With the increased
environmental awareness of the
past forty years, stormwater has become
regarded as more than simply displaced
rainwater. Urban runoff from impermeable
areas such as roads, storage areas,
and parking lots, has been recognized
to contain pollutants that can be toxic to
the natural environment. It is these pollutants
conveyed through urban runoff
that must be removed before the
stormwater is allowed to enter the natural
environment.
There are many types of stormwater
pollutants including hydrocarbons, suspended
solids, dissolved solids, and hydrocarbons.
The source of these materials
varies with each site; however, automobiles
are an obvious common
source on both road and parking lot
drainage areas. Mechanical wear, tire
wear, and corrosion are primary sources
for particulates and metals including,
lead, zinc, copper, cadmium, and chromium1.
The amount of metals discharged into
the environment in stormwater varies.
Studies conducted at a variety of locations
indicate high levels of metals in
stormwater runoff. Drapper et al.1 tested
road runoff at 21 sites in Southeast
Queensland, Australia. A study by Pitt
et al. (1995) 2 involved 56 tests conducted
on a number of different land
uses in Birmingham, Alabama, including
parking areas, road runoff, and landscaped
areas.
Table 1 - Comparison between water quality guidelines and stormwater runoff.
Table 1 compares the concentrations
of five metals between various North
American water quality regulations and
guidelines and the stormwater data collected
by these researchers. The comparison shows that levels of lead and
cadmium in runoff are above both the
United States and Ontario drinking water
standards. Although stormwater is
not a direct source of drinking water for
humans in North America, it often drains
to drinking water supplies and natural
environments causing harm to aquatic
organisms. Bioaccumulation of toxins
in nature eventually affects humans and
other creatures higher up in the food
chain.
Guidelines from B.C. provide additional
standards for interpreting results
by identifying various use categories
including aquatic life, livestock, and recreational.
These guidelines give an indication
of the sensitivity of different
water uses to metal concentrations.
Research data show that the concentrations
of cadmium, chromium and zinc
in stormwater runoff are well above the
recommended guidelines.
The effects of excessive metals in
drinking water can be as benign as an
unpleasant odour and taste and as severe
as kidney damage and physical or mental
development problems in children
(Table 2).
Undissolved metals found in
stormwater adhere to fine particulate
matter5. By removing these fine particles,
a large percentage of metals can
be prevented from entering the natural
environment, thereby minimizing the
impact to plants, animals and humans.
Urban runoff must be treated to prevent
further degradation of the natural environment,
minimize health risks, and reduce
bioaccumulation.
References
1 Drapper, D., R. Tomlinson, P. Williams.
An Investigation of the Quality of
Stormwater Runoff from Road Pavements;
A South-east Queensland Case
Study. School of Environmental Engineering,
Griffith University, Nathan
Campus, Queensland. 2 Pitt, R., R. Field, M. Lalor, and M.
Brown Urban, 1995. Urban stormwater
toxic pollutants: assessment, sources,
and treatability. Water Environment Research
Vol. 67, 260-274. 3 US EPA, Office of Water, Current
Drinking Water Standards, www.epa.gov/
safewater/mcl.html. 4 MOE, Ontario Drinking Water Objectives,
January 2001. Government of
Ontario, Queen’s Printer for Ontario. 5 Ball, J.E., R. Jenks and D. Aubourg,
1998. An assessment of the availability
of pollutant constituents on road surfaces.
Sci of the Tot Env 209 (1998):
243-254. 6 Ministry of Environment, Lands and
Parks Land Data BC, Geographic Data
BC for the Land Use Task Force Resources
Inventory Committee, Guidelines
for Interpreting Water Quality
Data, 1998. Province of British Columbia,
Resources Inventory Committee.
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