Waterborne Infectious Diseases

      Waterborne Infectious Diseases

Human infectious diseases are among the most serious effects of water pollution, especially in developing countries, where sanitation may be inadequate or non-existent. Waterborne diseases occur when parasites or other disease-causing microorganisms are transmitted via contaminated water, particularly water contaminated by pathogens originating from excreta. These include typhoid, intestinal parasites, and most of the enteric and diarrheal diseases caused by bacteria, parasites, and viruses. Among the most serious parasitic diseases are amoebiasis, giardiasis, ascariasis, and hookworm.

Developed countries are not immune to the problem of infectious waterborne diseases. In 1993, high cryptosporidium levels in Milwaukee's drinking water supply sickened more than 400,000 residents. That was an unusually extreme case, but transmission of disease agents such as bacteria and cysts via contaminated but poorly treated municipal water is more common than it should be. Every year, an estimated seven million Americans are sickened by contaminated water. This is only partly due to drinking water—contamination of recreational water (such as beach water) is also a problem.

WATER-RELATED DISEASES NOT RELATED TO WATER POLLUTION Water-based diseases are somewhat similar to water-borne diseases but are not typically an effect of water pollution. They come from infectious agents that naturally spend part of their life cycles in water. Humans can become infected when they drink or come in contact with the water that serves as home to these organisms . One of the most widespread examples in this category is schistosomiasis, which currently infects 200 million people in 74 countries. Similarly, diseases like malaria and dengue fever are spread by insects that breed or feed near water.

Every year there are thousands of beach closings in the US, and outdated monitoring methods may in some cases leave beachgoers vulnerable to a range of illnesses. Polluted beach water can cause rashes, ear aches, pink eye, respiratory infections, hepatitis, encephalitis, gastroenteritis, diarrhea, vomiting, and stomach aches. Hey, that's no day at the beach!

WATER POLLUTION EFFECTS – Category 2

Nutrient Pollution

The Woods Hole Oceanographic Institution calls nutrient pollution the most widespread, chronic environmental problem in the coastal ocean. The discharges of nitrogen, phosphorus, and other nutrients come from agriculture, waste disposal, coastal development, and fossil fuel use. Once nutrient pollution reaches the coastal zone, it stimulates harmful overgrowths of algae, which can have direct toxic effects and ultimately result in low-oxygen conditions.

Certain types of algae are toxic. Overgrowths of these algae result in "harmful algal blooms," which are more colloquially referred to as "red tides" or "brown tides." Zooplankton eat the toxic algae and begin passing the toxins up the food chain, affecting edibles like clams, and ultimately working their way up to seabirds, marine mammals, and humans. The result can be illness and sometimes death.

FIRST THE TIDE RUSHES IN, PLANTS A KISS ON THE SHORE ... The toxins found in brown-tide algae are strong enough that fishers can get skin lesions from exposure and coastal homeowners can be sickened from just the airborne toxins associated with a nearby brown tide.

Developed countries have started monitoring for toxic algal blooms, closing fisheries as necessary. This has reduced the incidence of related human illness but has had the obvious economic cost of lost income for fishers and related businesses—and it does nothing the solve the problem for the marine life stuck in the middle of the brown tide.

Nutrient-pollution-driven blooms of non-toxic algae and seaweed can also cause problems by reducing water clarity, making it hard for marine animals to find food and blocking the sunlight needed by sea grasses, which serve as nurseries for many important fish species.

When the algal overgrowths finally die, they sink to the bottom and begin decomposing. This process uses oxygen from the surrounding water. In some cases, the decomposition process takes enough oxygen out of the water that the level falls too low to support normal aquatic life and the region becomes a coastal dead zone.

Finally, nutrient pollution can trigger unusual outbreaks of fish diseases. For instance, scientists have found that Pfiesteria, a tiny marine pathogen, can thrive in nutrient-polluted waters. In 1991, one million menhaden fish in North Carolina's Neuse River were killed in a Pfiesteria outbreak. In 1997, several tidal creeks in the Chesapeake Bay watershed experienced Pfiesteria outbreaks, and serious fish kills occurred. Nutrient pollution played a role in both cases.

WATER POLLUTION EFFECTS – Category 3

Chemical Contamination

Over the years, many types of chemicals have gotten into our waterways—and they continue to do so today. Chemical water pollution typically occurs because ...

• the chemicals were dumped into the water intentionally;
• the chemicals seeped into groundwater, streams, or rivers because of failing pipes or storage tanks;
• the chemicals catastrophically contaminated waterways because of industrial accidents;
• the pollution settled out of polluted air (or was precipitated out of polluted air); or
• chemicals were leached out of contaminated soil.

The above types of chemical contamination are considered "point sources" of water pollution. Non-point-source chemical pollution also occurs via pesticide runoff from farm fields and homeowners' lawns, as well as runoff of automotive fluids and other chemicals from roads, parking lots, driveways, and other surfaces.

It's beyond the scope of this article to document the effect of every chemical that has ever polluted water, but it's easy enough to point out a few things:

• Severe chemical spills and leaks into surfaces waters usually have an immediate effect on aquatic life (fish kills, etc.).
• Chronic lower-level chemical pollution has more subtle effects, with problems manifesting over a long period of time and sometimes being difficult to tie directly to the water pollution.
• The human effects of chemical pollution in water can generally be viewed the same as any other form of chemical contamination—water is just the delivery mechanism.

There are a few broad categories of water pollution effects related to chemicals that are worth exploring further, which we do below.

Pesticides

Pesticides are carried in rainwater runoff from farm fields, suburban lawns, or roadside embankments into the nearest creeks and streams. Occasionally they are even intentionally sprayed into waterways as part of a pest-control effort. Egad—talk about destroying the village to save it!

Here are some noteworthy examples of the effects of pesticide water pollution:

• The US EPA has found widespread contamination of waterways by Atrazine, the second most commonly used herbicide in the US. Atrazine causes feminization of male frogs even at concentrations in water as low as 0.1 part per billion. Atrazine water pollution has been noted in many countries, including South Africa, Germany, and Denmark. The Natural Resources Defense Council notes that studies indicate the chemical may be linked to a number of human cancers, including prostate cancer and non-Hodgkin's lymphoma. A University of California San Francisco study found that Atrazine can affect human reproductive and developmental processes by disrupting human hormone activity. The effect occurs at concentrations as low as 2 ppb.
• Glyphosate (Roundup), another of the world's most common herbicides, was found to cause a 70% decline in frog biodiversity and an 86% decline in the total mass of tadpoles when the glyphosate got into water.
• Pesticides have been found in well water in countries such as India, The Netherlands, Italy, Israel, Japan, Canada and Australia, and the US. Pesticide contamination of drinking water is a particular problem in rural agricultural areas where pesticide use is heavy and drinking water supplies come directly from groundwater or surface water.
• Pesticides can migrate via water into the food chain as well, ultimately being consumed by humans or animals in food.
• In the most infamous case of pesticide pollution, widespread use of the insecticide DDT polluted waterways, contaminating fish, and ultimately poisoning bald eagles (and other animals) that ate the fish. DDE, the principal breakdown product of DDT, built up in the fatty tissues of female eagles and prevented sufficient calcium being released to produce strong egg shells. The thin shells would break when the parents sat on the eggs to keep them warm. DDT affected many other species as well. The case against DDT and other pesticides was first introduced in the classic book by Rachel Carson, Silent Spring.  (ALSO SEE: Related GP article about the potential un-banning of DDT: DDT and Malaria.)
• In terms of general human health effects, pesticides can ...
  • affect and damage the nervous system;
  • cause liver damage;
  • damage DNA and cause a variety of cancers;
  • cause reproductive and endocrine damage;
  • cause other acutely toxic or chronic effects.

Oil and Petroleum Chemicals

When oil pollution gets in water, some of the components of are degraded and dispersed by evaporation, photochemical reactions, or bacterial degradation, while others are more resistant and may persist for many years, especially in shallow waters with muddy sediments.

Though much scientific work remains to be done on the effect that petroleum pollution has on plants and animals, we do know a few things:

Exposure to oil or its constituent chemicals can alter the ecology of aquatic habitats and the physiology of marine organisms. Scientists know that oil (or chemical components of oil) can seep into marsh and sub-tidal sediments and lurk there for decades, negatively affecting marsh grasses, marine worms, and other aquatic life forms that live in, on, or near the sediment. Evidence strongly suggests that components of crude oil, called polycyclic aromatic hydrocarbons (PAHs), persist in the marine environment for years and are toxic to marine life at concentrations in the low parts-per-billion range. Chronic exposure to PAHs can affect development of marine organisms, increase susceptibility to disease, and jeopardize normal reproductive cycles in many marine species.

WE PREFER THE JAVA OF JUAN VALDEZ TO THE OIL OF EXXON VALDEZ Before the Exxon Valdez oil spill, the effects of the pollution were thought to be relatively short-term—a year or two. The effects of the Valdez, however, lasted up to 8 or 9 years, and in some ways still persist today. The oil has persisted in small quantities below the surface in the coarse intertidal sediments, out of reach of the wave action and sunlight needed to break down the oil. Studies have found that marine mammals, sea ducks, and some fish species suffered high mortality for years after the spill because they ate invertebrates contaminated by the hidden oil or ate oil directly while foraging. Studies of pink salmon showed that exposure early in life to small amounts of oil—as low as a few parts per billion—led to stunted growth and higher mortality rates.

MTBE, a gas additive, has contaminated many groundwater sources in the US. Animal studies suggest that ingestion of MTBE causes gastrointestinal irritation, liver and kidney damage, and nervous system effects.

Mercury

Mercury finds its way into water primarily through air pollution from coal-fired power plants and some other industrial processes. In the water, the elemental mercury is converted to methylmercury by certain bacteria, after which it moves up the food chain of fish gobbling each other up. In then end, the larger fish may end up on your dinner plate—swordfish, sea bass, marlin, halibut, or tuna, for example. (For more information on this specific angle of mercury-in-water pollution effects, see our article on Mercury in Fish.)

The effects of mercury on humans are already pretty well understood. However, the more we learn, the worse the news gets, and US EPA keeps lowering its "safe exposure level." Young children and fetuses are most at risk because their systems are still developing. Exposure to mercury in the womb can cause neurological problems, including slower reflexes, learning deficits, delayed or incomplete mental development, autism, and brain damage. Mercury in adults is also a problem, causing:

• central nervous system effects like Parkinson's disease, multiple sclerosis, and Alzheimer's disease;
• heart disease;
• and, in severe cases, causing death or irreversibly damaging areas of the brain.

Animals in any part of the food chain affected by the bioaccumulation of mercury can also suffer the effects of mercury pollution. Possible effects include death, reduced reproduction, slower growth and development, and abnormal behavior.

PCBs, Dioxins, and Other POPs

PCBs, dioxins, DDT, and a number of other persistent organic pollutants don't readily break down in the environment and tend to collect in the fatty tissues of animals. All of these chemicals are toxic for the animals that harbor them. In cases where humans might eat, say, a PCB-contaminated farmed salmon, their systems must deal with the chemical insult.

Here are a few specific examples of the effects of POPs-related water pollution:

• PCB contamination in Puget Sound exceeds the level known to suppress immune function in the harbor seal. PCBs are also thought to be a factor in the decline of Puget Sound killer whales, whose numbers declined by 14% between 1995 and 2003.
• Elevated levels of PCBs and DDT may be contributing to the deaths of California southern sea otters.
• The breeding success of Baltic seals declined sharply in the 1960s and 1970s. Scientists suspect that PCBs were the main culprit.
• Deformed fish and other aquatic life have been found near Swedish pulp mills that use chlorine as a bleaching agent—a practice that results in discharges of dioxins and other highly toxic substances.

Other Chemicals

Tens of thousands of chemicals are used in industrial processes and are found in car-maintenance products, household cleaners, toiletries, and many other consumer products. Our current regimes for controlling whether these chemicals get into the environment are not sufficient for keeping them out of the water, and the potential myriad effects are worrisome.

It's well understood that many chemicals can have direct toxic effects on aquatic life. Industrial spills into rivers invariable kill fish for miles downstream. But chronic chemical pollution in waterways is an even bigger problem. The number of US river miles on which people have been advised to restrict their consumption of fish consumption of fish has risen sharply in the last two decades, and most states routinely issue advisories on consumption of fish from rivers and streams. (Check your state here.)

A newly emerging threat is the hormone-disrupting character of many chemicals. For instance, chemicals contained in sewage discharges into the waters off the Southern California coast are thought to be responsible for "intersex" fish. Similarly, chemicals in the water are also thought the be responsible for egg-growing male fish in Maryland's Potomac River—possibly the effect of excreted birth-control chemicals.

More generally, the effects of hormone-disrupting chemicals include interrupted sexual development; thyroid system disorders; inability to breed; reduced immune response; and abnormal mating and parenting behavior. In humans, endocrine disruptors are thought to lead to degraded immune function, mental impairment, decreased fertility, and increases in some types of cancers.

“ENGAGE THE GLOBAL TOXIFICATION WEAPON!” SCREAMED THE KLINGON COMMANDER For a more general treatment of the problem of "global toxification" from chemical pollution, see our article onhormone disruptors.

WATER POLLUTION EFFECTS – Category 4

Mining

There are a number of negative water-pollution effects from mining operations:

Acid mine drainage: When rain or surface water flows over exposed rock and soil, it can combine with naturally occurring sulfur to form sulfuric acid. The acidified rainwater eventually finds its way to streams and groundwater, polluting them and impacting local aquatic life. Some streams can become so acidic—more acidic than car-battery acid—the aquatic ecosystem is completely destroyed. The same leaching process that causes acid mine drainage can impart heavy-metal pollutants from the soil and rock as well.

Spills and leaks:Whether it's a leak in the containment system of a cyanide leach heap or a breach in a coal-slurry impoundment dam, the result is the same—pollution of streams, rivers, and groundwater, killing aquatic life and poisoning drinking water. Mountaintop Removal Mining: In this technique, the tops of coal-rich mountains are removed and the overburden is dumped into nearby valleys, burying stream habitats altogether, with the obvious catastrophic effect on whatever life forms lived in or around the stream.

WATER POLLUTION EFFECTS OF MINING DISASTERS In 2000, a tailings dam split open at the Baia Mare mine in Romania. This accident sent some 100,000 tons of wastewater and 20,000 tons of sludge contaminated with cyanide, copper, and heavy metals into the Tisza River, and eventually into the Danube—destroying 1,240 tons of fish and polluting the drinking water supplies of 2.5 million people. In 2008 in the US state of Tennessee, an impoundment dam failed and 5.4 million cubic yards of coal ash spilled into adjacent waterways, killing fish, damaging property, and threatening drinking-water supplies. Residents now face concerns about the long-term health effects from the ash, which contains numerous harmful contaminants such as arsenic. It should be noted that in this case the spill was not related to coal mining; it was stored coal ash, the waste that results from burning coal in a power plant. [SOURCES: Worldwatch Institute, Lexington Herald-Leader, Los Angeles Times]

WATER POLLUTION EFFECTS – Category 5

Marine Debris

Marine debris is basically trash in the ocean. Trash fouls inland waterways too, for sure, but trash seems to be a particular problem in our seas. The Ocean Conservancy calls marine debris one of the world's most pervasive marine pollution problems.

The debris includes escaped inland trash and garbage thrown overboard by ships and boaters—plastic bottles and bags, six-pack rings, cigarette butts, Styrofoam, etc. Marine animals can swallow the trash items, which often look similar to prey they would normally eat, or the trash item may have barnacles or other delectables attached and is inadvertently ingested with the food. For instance, sea turtles will eat a plastic bag believing it to be a jellyfish. The bag can cause an intestinal blockage and sometimes death.

A new and potentially devastating effect of marine debris is emerging. After years of degradation at sea, plastic breaks up. The plastic has not biodegraded but rather has disintegrated into very small pieces. Marine animals near the bottom of the food chain are now ingesting these teeny-tiny little pieces of plastic pollution. How far up the food chain the stuff will go is unknown.

Discarded or lost fishing gear—line, rope, nets—and certain trash items can get wrapped around marine animals fins or flippers, causing drowning or amputation. Marine debris can also degrade coral reefs, sea grass beds, and other aquatic habitats.

WATER POLLUTION EFFECTS – Category 6

Thermal Pollution

It's easy enough to see how discharging the heated-up water from a power plant into a river could cause problems for aquatic organisms used to having their water home stay at a fairly specific temperature. Indeed, industrial thermal pollution is a problem for our waterways—fish and other organisms adapted to a particular temperature range can be killed from thermal shock, and the extra heat may disrupt spawning or kill young fish.

Additionally, warmer water temperatures lower the dissolved oxygen content of the water. That's a double-whammy to aquatic organisms, since the warmer water also causes them to increase their respiration rates and consume oxygen faster. All this increases aquatic organisms' susceptibility to disease, parasites, and the effects of toxic chemicals.

Global warming is imparting extra heat to our oceans, which have absorbed about 20 times as much heat as the atmosphere over the past half-century. The ocean is a complex system, and scientists don't know yet what all of the effects of this type of "water pollution" will be, but here are some likely ones: Sea levels will rise (because of thermal expansion and melting ice), increasing coastal flooding and inundation. There will be more intense hurricanes as they gather additional strength from warmer surface waters. Temperature-sensitive species like corals will see tougher times. Over the last 2-3 decades, temperatures in tropical waters have increased nearly 1 degree Fahrenheit. That may not sound like much, but it's been enough to increase cases of coral bleaching. A study in Science estimated that if carbon dioxide releases continue at the current rate, by mid-century ocean conditions (increased water temperatures + increased ocean acidity) will make it impossible for most corals to survive. Increasing sea-surface temperatures are associated with the northward spread of a oyster pathogen in the eastern US. Similar cases are highly likely.

CLIMATE CHANGE — CONVEYOR OF HYPOXIA The movie The Day After Tomorrow dramatized what might happen to North America if global warming shut down the oceanic conveyor belt. In reality, Northern Europe would be much more in the crosshairs of such an event, but marine species in the deep ocean that now get their oxygen supplies from sinking surface water could also be highly affected. More generally, warmer water has less oxygen-holding capacity than colder water. The oceans have already warmed 1 degree on average—and the trend is still up. In a related issue, warming-driven changes in the oceans' thermohaline circulation could increase the risk of hypoxia in the deep ocean. Related GP article: The Day After Tomorrowscience

Water Pollution Effects – Category 7

Noise Pollution

"Noise pollution" from ship engines and sonar systems make it difficult for marine mammals like whales, dolphins, and porpoises to communicate, find food, and avoid hazards. Powerful sonar systems operating at certain frequencies have been implicated in whale beachings and may cause damage to marine mammals' sound-sensitive internal structures, causing internal bleeding and even death.

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Frequent or chronic exposure to both high- and low-intensity sounds may cause stress on all higher forms of marine life, potentially affecting growth, reproduction, and ability to resist disease.

WATER POLLUTION EFFECTS – Category 8

Costs to Consumers

Tap water quality is regulated, and nearly 100% of community water systems in the US are meeting clean drinking water standards. But is that good enough? Why are so many people convinced it's worth buying bottled water?

When the Environmental Working Group tested tap water from a number of cities, it found 119 "normal" chemicals—those for which the EPA has set health-based limits—and another 141 completely unregulated chemicals. If tap water has that many chemicals in it but is still classified as meeting water quality standards, one might say that the standards are, um, lax.

If nothing else, it's fair to say that even "safe" tap water usually has a "chloriney" taste. Chlorine and its disinfection byproducts are known health threats, and none of us wants to be the victim of the next cryptosporidium-in-drinking-water problem or some similar nightmare.

So it's no wonder many of us go to the extra expense and trouble of buying bottled water or using water filters, even though there are no regulations that guarantee those approaches will provide water that is safer.

We should not accept this situation passively. It's costing us LOTS of money. The bill for bottled water is about $12 billion annually—in the US alone. And you can add purchases of kitchen-sink water filters on top of that. Add in the extra fueluse (and air pollution) associated with manufacturing, packaging, and transporting these products, and we see that the cost of trying to avoid polluted tap water is rather high. Heck, we didn't even count the health costs associated with waterborne diseases and other health problems due to water pollution.

Suppose we as a society were to spend even half of this money instead on addressing the causes of water pollution. It would go a long way toward fixing aging water treatment plants; funding wetlands restorations and watershed monitoring efforts; and beefing up enforcement of clean-water laws.