What Kind of Chemical Pollutants Pollute Water?

Water pollution comes from many forms: erosion sediment, effluent or bacteriological contaminants, trash and chemicals. Out of the four, chemicals can have the worst effects and the biggest impact. The water system has the ability to handle reasonable quantities of sediment and effluent, and trash can be filtered out. Chemical pollution, since the sources are so varied, can be more difficult to remove and neutralize. There are numerous types of chemicals that pollute water.

Fertilizers

• One of the worst chemical pollution sources in water comes from farm and garden runoff, and contains pesticides, herbicides and fertilizers. Even if they are not toxic on their own, fertilizers increase the amount of nitrates and phosphorus in the water, which encourages the growth of plants that clog waterways, block needed light and steal oxygen from the water.

Pesticides

• Pesticides and herbicides are toxic and can harm organisms at every stages of the food chain. DDT (dichlorodiphenyltrichloroethane), for example, is a synthetic pesticide that entered the waterways from farm runoff, before it was banned in the United States in 1972. DDT in waterways poisoned fish, who either died or stored the poison in their bodies. The die-off of fish reduced the available food supply for animals higher on the food chain. Eating poisoned fish led to birth defects and developmental issues in many prey animals. DDT caused fatal birth defects in bald eagles that almost lead to their extinction.

Household

• Toxic household chemicals enter the water through wastewater, such as household greywater (water from sinks and washers) or storm drains. Many cleaners, like ammonia and detergents, are alkaline and raise the pH of the water above neutral levels. Changes in pH affect the microorganisms in the water by creating an inhospitable environment. Many of these microorganisms clean pollutants from the water, and release oxygen, through their biological actions. These benefits are lost if the organisms die off.

  Solvents like formaldehyde and acids used for cleaning, such as oxalic acid and hydrochloric acid, are corrosive or can build up in the bodies of fish and shellfish, in turn poisoning the animals that eventually feed on them, including humans.

Industrial

• Industrial chemicals and chemical byproducts are plentiful and cause a wide variety of health issues like cancer and damage to the nervous system. PAHs (Polycyclic aromatic hydrocarbons), for example, are byproducts of burning fossil fuels, and enter the water through runoff from roadways and from the air. PAHS are known to cause cancer in very small quantities. Paint, oil, grease, and the solvents used along with them, can suffocate fish and are toxic to aquatic life, either killing organisms outright, or causing developmental or reproductive issues.

Metals

• Heavy metals like lead, mercury, barium and manganese build up in the soil and in the bodies of aquatic life, especially bottom feeders such as clams, slowly poisoning them and the creatures that feed on them. The effect is cumulative as one species consumes another on up the food chain, each adding its own contribution to the store of mercury inside a fish's body. Large aquatic predators such as tuna and swordfish can carry dangerous doses of mercury in a single serving. Lead and mercury both cause neurological damage and developmental issues. Mining runoff is a major source for these metals.