The Ecology Book

234

from fossil-fuel-burning power

stations, factories, motor vehicles,

the burning of wood and dung for

heat and cooking fuel, and methane

from cattle, landfill sites, and

fertilized fields. Poor air quality

damages human health and crops,

and some fossil-fuel emissions cause

acid rain, which has killed forests

and fish in thousands of lakes.

The World Health Organization

(WHO) estimates that nine out of

ten people worldwide are breathing

polluted air, causing widespread

illness and allergies. Furthermore,

some aerosols, depending on the

composition and color of the

particles, block the amount of solar

radiation reaching Earth’s surface,

thus having a cooling effect on the

planet. Efforts to reduce air

pollution can therefore make the

effects of global warming worse.

Rivers, lakes, and seas

Surface water, groundwater, and the

oceans become contaminated by

toxic chemicals from industry, from

chemical runoff from farmland, from

general trash such as plastics, and

from human waste.

Some rivers and lakes are

so polluted that they can support

no life at all, deprive communities

of freshwater and food, and carry

a risk of waterborne diseases, such

as polio, cholera, dysentery, and

typhoid. The WHO estimates that

2 billion people worldwide are

drinking water contaminated with

human waste, resulting in the

deaths of 500,000 people a year.

POLLUTION

In the oceans, the most acutely

destructive pollution has resulted

from disasters involving oil tankers

and oil terminals. When the Exxon

Va ldez supertanker broke up on

rocks off the coast of Alaska in 1989,

11 million gallons (50 million liters)

of crude oil were released into the

North Pacific. The oil smothered or

Orcas may become extinct as a result

of PCB (polychlorinated biphenyl)

pollutants. The compound becomes

more concentrated higher in the food

chain, and orcas are apex predators.

Pollutants entering

the oceans

10%

10%

5%

5%

30%

20%

20%

Farmland runoff

Sewage

Litter

Offshore oil

Industrial

wastewater

Maritime

transportation

Air pollutants

Pollution is one of the

biggest problems we are

facing globally, with horrible

future costs to society.

Maria Neira

US_230-235_Pollution.indd 234 12/11/18 6:25 PM