Water pollution occurs when harmful
substances-often chemicals or
microorganisms-contaminate a stream,
river, lake, ocean, aquifer, or other body of
water, degrading water quality and rendering
it toxic to humans or the environment.
This widespread problem of water pollution
is jeopardizing our health. Unsafe water kills
more people each year than war and all other
forms of violence combined. Meanwhile, our
drinkable water sources are finite: Less than
1 percent of the earth's freshwater is actually
accessible to us. Without action, the
challenges will only increase by 2050, when
global demand for freshwater is expected to
be one-third greater than it is now.
Water is uniquely vulnerable to pollution.
Known as a "universal solvent" water is able
to dissolve more substances than any other
liquid on earth. It's the reason we have Kool-
Aid and brilliant blue waterfalls. It's also why
water is so easily polluted. Toxic substances
from farms, towns, and factories readily
dissolve into and mix with it, causing water
pollution.
Here are some of the major sources of water
pollution worldwide:
Used water is wastewater. It comes from our
sinks, showers, and toilets (think sewage)
and from commercial, industrial, and
agricultural activities (think metals, solvents,
and toxic sludge). The term also includes
stormwater runoff, which occurs when
rainfall carries road salts, oil, grease,
chemicals, and debris from impermeable
surfaces into our waterways
More than 80 percent of the world's
wastewater flows back into the environment
without being treated or reused, according to
the United Nations; in some least-developed
countries, the figure tops 95 percent. In the
United States, wastewater treatment
facilities process about 34 billion gallons of
wastewater per day. These facilities reduce
the amount of pollutants such as pathogens,
phosphorus, and nitrogen in sewage, as well
as heavy metals and toxic chemicals in
industrial waste, before discharging the
treated waters back into waterways. That's
when all goes well. But according to EPA
estimates, our nation's aging and easily
overwhelmed sewage treatment systems
also release more than 850 billion gallons of
untreated wastewater each year.
Big spills may dominate headlines, but
consumers account for the vast majority of
oil pollution in our seas, including oil and
gasoline that drips from millions of cars and
trucks every day. Moreover, nearly half of the
estimated 1 million tons of oil that makes its
way into marine environments each year
comes not from tanker spills but from land-
based sources such as factories, farms, and
cities. At sea, tanker spills account for about
10 percent of the oil in waters around the
world, while regular operations of the
shipping industry-through both legal and
illegal discharges-contribute about one-
third. Oil is also naturally released from
under the ocean floor through fractures
known as seeps.
Radioactive waste is any pollution that emits
radiation beyond what is naturally released
by the environment. It's generated by
uranium mining, nuclear power plants, and
the production and testing of military
weapons, as well as by universities and
hospitals that use radioactive materials for
research and medicine. Radioactive waste
can persist in the environment for thousands
of years, making disposal a major challenge.
Consider the decommissioned Hanford
nuclear weapons production site in
Washington, where the cleanup of 56 million
gallons of radioactive waste is expected to
cost more than $100 billion and last through
2060. Accidentally released or improperly
disposed of contaminants threaten
groundwater, surface water, and marine
resources.
Point source pollution
When contamination originates from a single
source, it's called point source pollution.
Examples include wastewater (also called
effluent) discharged legally or illegally by a
manufacturer, oil refinery, or wastewater
treatment facility, as well as contamination
from leaking septic systems, chemical and
oil spills, and illegal dumping. The EPA
regulates point source pollution by
establishing limits on what can be
discharged by a facility directly into a body of
water. While point source pollution originates
from a specific place, it can affect miles of
waterways and ocean.
