Learning Objectives

• Discuss the risks that water pollution poses to human and environmental health.
• Explain where fresh and saltwater pollution come from.
• Discuss how pathogen born diseases are caused by water pollution.
• Describe why conserving water and protecting water quality is important to human health and the environment.
• Describe how water pollution reduces the amount of safe drinking water available.
• Discuss who is responsible for preventing and cleaning up water pollution.

Vocabulary

• thermal pollution

Introduction

Freshwater and ocean pollution are serious global problems that affect the availability of safe drinking water, human health, and the environment. Waterborne diseases from water pollution kill millions of people in undeveloped countries every year.

Sources of Water Pollution

Water pollution contributes to water shortages by making some water sources unavailable for use. In underdeveloped countries, raw sewage is dumped into the same water that people drink and bathe in. Even in developed countries, water pollution affects human and environmental health. Water pollution includes any contaminant that gets into lakes, streams, and oceans. The most widespread source of water contamination in developing countries is raw sewage. In developed countries, the three main sources of water pollution are described below.

KQED: Mercury in San Francisco Bay

Mercury, a potent neurotoxin, has been flowing into the San Francisco Bay since the Gold Rush Era. It has settled in the bay’s mud and made its way up the food chain, endangering wildlife and making many fish unsafe to eat. Now a multi-billion-dollar plan aims to clean it up. Learn more at: http://science.kqed.org/quest/video/mercury-in-san-francisco-bay/.

Municipal Pollution

Wastewater from cities and towns contains many different contaminants from many different homes, businesses, and industries (Figure below). Contaminants come from:

• Sewage disposal (some sewage is inadequately treated or untreated).
• Storm drains.
• Septic tanks: sewage from homes.
• Boats that dump sewage.
• Yard runoff (fertilizer and herbicide waste).

Industrial Pollution

Factories and hospitals spew pollutants into the air and waterways (Figure below). Some of the most hazardous industrial pollutants include:

• Radioactive substances from nuclear power plants, medical and scientific sources.
• Heavy metals, organic toxins, oils, and solids in industrial waste.
• Chemicals, such as sulfur, from burning fossil fuels.
• Oil and other petroleum products from supertanker spills and offshore drilling accidents.
• Heated water from industrial processes, such as power stations.

Agricultural Pollution

Runoff from crops, livestock, and poultry farming carries contaminants such as fertilizers, pesticides, and animal waste into nearby waterways (Figure below). Soil and silt also runs off farms. Animal wastes may carry harmful diseases, particularly in the developing world.

Fertilizers that run off of lawns and farm fields are extremely harmful to the environment. Nutrients, such as nitrates, in the fertilizer promote algae growth in the water they flow into. With the excess nutrients, lakes, rivers, and bays become clogged with algae and aquatic plants. Eventually these organisms die and decompose. Decomposition uses up all the dissolved oxygen in the water. Without oxygen, large numbers of plants, fish, and bottom-dwelling animals die.

Every year dead zones appear in lakes and nearshore waters. A dead zone is an area of hundreds of kilometers of ocean without fish or plant life (Figure below).

The Mississippi is not the only river that carries the nutrients necessary to cause a dead zone. Rivers that drain regions where human population density is high and where crops are grown create dead zones all over the world (Figure below).

Ocean Pollution

Most ocean pollution comes as runoff from land and originates as agricultural, industrial, and municipal wastes (Figure below). The remaining 20% of water pollution enters the ocean directly from oil spills and people dumping wastes directly into the water. Ships at sea empty their wastes directly into the ocean, for example.

Coastal pollution can make coastal water unsafe for humans and wildlife. After rainfall, there can be enough runoff pollution that beaches must be closed to prevent the spread of disease from pollutants. A surprising number of beaches are closed because of possible health hazards each year.

A large proportion of the fish we rely on for food live in the coastal wetlands or lay their eggs there. Coastal runoff from farm waste often carries water-borne organisms that cause lesions that kill fish. Humans who come in contact with polluted waters and affected fish can also experience harmful symptoms. More than one-third of the shellfish-growing waters of the United States are adversely affected by coastal pollution.

A National Geographic video, Why the Ocean Matters, has beautiful footage and a brief introduction to some of the problems facing the seas: http://video.nationalgeographic.com/video/player/environment/.

The Gulf of Mexico Oil Spill

New drilling techniques have allowed oil companies to drill in deeper waters than ever before. This allows us to access oil deposits that were never before possible but with great technological difficulty. The risks from deepwater drilling and the consequences when something goes wrong are greater.

Working on oil platforms is dangerous and workers are exposed to harsh ocean conditions and gas explosions. The danger was never more obvious than on April 20, 2010, when 11 workers were killed and 17 injured in an explosion on a deepwater oil rig in the Gulf of Mexico (Figure below). The drilling rig, operated by BP, was 77 km (48 miles) offshore and the depth to the well was more than 5,000 feet.

Two days after the explosion, the drill rig sank. The 5,000-foot pipe that connected the wellhead to the drilling platform bent. Oil was free to gush into the Gulf of Mexico from nearly a mile deep (Figure below). Initial efforts to cap or contain the spill at or near its source all failed to stop the vast oil spill. It was not until July 15, nearly three months after the accident, that the well was successfully capped.

Estimating the flow of oil into the Gulf from the well was extremely difficult because the leak was so far below the surface. The U.S. government estimates that about 4.9 million barrels entered the Gulf at a rate of 35,000 to 60,000 barrels a day. The largest previous oil spill in the United States was of 300,000 barrels by the Exxon Valdez in 1989 in Prince William Sound, Alaska.

Once the oil is in the water, there are three types of methods for dealing with it:

1. Removal: Oil is corralled and then burned; natural gas is flared off (Figure below). Machines that can separate oil from the water are placed aboard ships stationed in the area. These ships cleaned tens of thousands of barrels of contaminated seawater each day.

2. Containment: Floating containment booms are placed on the surface offshore of the most sensitive coastal areas in an attempt to attempt to trap the oil. But the seas must be calm for the booms to be effective, and so were not very useful in the Gulf (Figure below). Sand berms have been constructed off of the Louisiana coast to keep the oil from reaching shore.

3. Dispersal: Oil disperses naturally over time because it mixes with the water. However, such large amounts of oil will take decades to disperse. To speed the process up, BP has sprayed unprecedented amounts of chemical dispersants on the spill. That action did not receive support from the scientific community since no one knows the risks to people and the environment from such a large amount of these harmful chemicals. Some workers may have become ill from exposure to the chemicals.

BP drilled two relief wells into the original well. When the relief wells entered the original borehole, specialized liquids were pumped into the original well to stop the flow. Operation of the relief wells began in August 2010. The original well was declared effectively dead on September 19, 2010.

The economic and environmental impact of this spill will be felt for many years. Many people rely on the Gulf for their livelihoods or for recreation. Commercial fishing, tourism, and oil-related jobs are the economic engines of the region. Fearing contamination, NOAA imposed a fishing ban on approximately one-third of the Gulf (Figure below). Tourism is down in the region as beach goers find other ways to spend their time. Real estate prices along the Gulf have declined precipitously.

The toll on wildlife is felt throughout the Gulf. Plankton, which form the base of the food chain, are killed by the oil, leaving other organisms without food. Islands and marshlands around the Gulf have many species that are already at risk, including four endangered species of sea turtles (Figure below). With such low numbers, rebuilding their populations after the spill will be difficult.

The Gulf of Mexico is one of only two places in the world where bluefin tuna spawn and they are also already endangered. Marine mammals in the Gulf may come up into the slick as they come to the surface to breathe (Figure below).

Eight national parks and seashores are found along the Gulf shores. Other locations may be ecologically sensitive habitats such as mangroves or marshlands (Figure below).

This story is a long way from being over.

Thermal Water Pollution

Thermal pollution is any rise or fall in water temperatures that is not weather related. Power plants cool heated equipment with local streams, lakes, or ocean water and then return that heated water back into the environment. Cold water pollution is observed when very cold water is released from reservoirs. Aquatic organisms are often sensitive to even small temperature changes. The Macquarie perch is now extinct in most of its upland river habitats partially because of thermal pollution by dams.

Lesson Summary

• Industrial, agricultural, and municipal sources produce harmful water pollutants such as toxic chemicals, radiological agents, and animal wastes.
• Deep water oil drilling presents an enormous threat to the economic and ecological health of the oceans as seen in the Gulf Oil Spill of 2010.

Review Questions

1. How does water pollution contribute to water shortages?

2. How are the major sources of water pollution different between developing and developed countries?

3. Where are most of the dead zones located?

4. Explain what a dead zone is.

5. Why are coastal wetlands important and what are the sources of pollution that affects them?

6. What is the leading cause of death for children around the world?

7. What are the risks of deepwater drilling for petroleum?

8. Months after the oil spill the amount of oil that is located at the top of the Gulf water and on the shorelines is much less than the amount that was predicted to be in those locations. What happened to the oil? Did id just disappear? Does this mean that the dire predictions being made just after the spill were wrong?

Points to Consider

• How does water pollution reduce the amount of drinking water available for people to use?
• About 50% of all infectious diseases are caused by water pollution. What can be done to reduce the number of pathogens that reach our fresh water supplies?
• Ocean pollution harms some of the most productive sources of marine life. How can we change our behaviors to protect marine life?