DANGEROUS WATERS



DANGEROUS WATERS

Twenty percent of the people on Earth don’t have access to clean water and that number is likely to increase. And not only is access to freshwater a major problem for huge populations of people around the world, but so is the condition of the water when it finally trickles down people’s throats. Infectious pathogens (anything that can cause a disease) and harmful chemicals—from parasites to poisons—contaminate the world’s freshwater and contribute to the deaths of millions of people worldwide every year. Understanding how these contaminants work and how we are exposed to them holds the key to protecting our drinking water and creating successful water treatment systems.

Around the world nearly 2 million people—most of them children under five—die every year from diarrheal diseases. That number is not surprising when you realize just how much dirty water flows in rivers or lies as still water (like in lakes and ponds) across the continents. Nearly 20 percent of the 6.6 billion people in the world lack a supply of clean water, and 40 percent lack safe sanitation facilities.

The battle for safe water is not easy. As quickly as new types of filters and water-transport systems are created, new contaminants and diseases are found as populations grow and the need for more water increases. Certain micro-organisms (microscopic organisms) can be hard to find in water samples and can cause severe illness at doses as low as only one infectious organism per drink of water. And those disease-causing organisms don’t stand still while we figure out how to combat them. As areas of dirty water increase in the world, they can lead to diseases getting more powerful and causing diseases that are harder to treat. Battling, let alone eliminating, those ever-changing organisms seems only to be getting more difficult.

One thing will never change: people need water for survival and it is as much as 70 percent of our body weight. Although we may survive four weeks without food, our bodies last, at best, only a few days without water. Furthermore, we use water for the most basic daily activities: drinking, cooking, bathing, washing, and sanitation. Diseases are not just gotten from drinking contaminated water. Poor personal hygiene from a lack of water can cause diseases like trachoma, a condition that can cause blindness and today affects 6 million people.

The discovery of chlorine as a microbe (single-celled organism) killer in the early 1900s was a turning point in drinking-water treatment. That, in turn, led to a major advance in public health. Chlorination was started in the United States around 1910, and during the next several decades the previously high mortality rate from typhoid fever—twenty-five deaths per 100,000—dropped to almost zero. Although chlorine easily destroys viruses and bacteria, though, it doesn’t work as well with some protozoan oocysts (developing cells), such as those of Cryptosporidium parvum—an agent of diarrheal disease. Another, and perhaps even nastier, drawback is that chlorine when mixed with other products in the treatment plant may create cancer causing by-products. Nevertheless, chlorine is still one of the cheapest and most effective disinfectants in use today.

Water shortages go hand in hand with disease. As freshwater becomes hard to find worldwide, waterborne disease agents and other contaminants become harder to control. Often the quantity of available water often matters more than the quality. In other words people will drink contaminated water just to stay alive if that is all they can get.

Every person, every day, needs at least thirteen gallons of water for drinking, cooking, bathing, and sanitation. In 1990 more than a billion of the world’s people used less than that. In the U.S. an average person's daily intake is more than 150 gallons a day.

All that water filling swimming pools and soaking gardens might seem extraordinarily wasteful, but only 8 percent of the planet’s freshwater supply goes toward personal, household, and city water use. Agriculture accounts for 70 percent, and industry for 22 percent, of current freshwater use. It takes more than fifty gallons of water to produce a single cup of milk, a quarter-pound hamburger takes 470 gallons and a cotton T-shirt uses 520 gallons. Consider how many cotton T-shirts are tucked away in your closets. It’s no surprise there is more demand than supply.

Daily water needs are exceedingly hard to meet in areas where sudden city growth is taking place. Out of date water-supply systems are simply not able to provide enough water and sanitation to people living in over-crowded cities. About half the world’s people are now city dwellers. This population increase puts great stress on the city’s water and sewage pipes, increasing the likelihood that people will make illegal connections into the water systems and very often allow contaminates to work their way into the city’s water supply.

Countries with sudden increases in city populations often face severe microbial hazards. In countries where water treatment plants cannot supply enough clean water to keep up with the increased number of people, roughly 200 children under the age of five die every hour from a water microbial infection. Many of the infections are caused by drinking water contaminated with human or animal feces that carry bacteria, viruses, protozoa, or worms. That’s the usual, but not the only, way waterborne diseases spread.

Exposure to contaminated water goes beyond the drinking fountain. Many diseases can spread by person-to-person contact or through food preparation, rather than actually drinking contaminated water.

For example, malaria-carrying mosquitoes use stagnant water (lakes, ponds) as a breeding ground; Giardia infection can be gotten during a swim in a local lake; clothing or bedding may carry parasitic mites; noroviruses can be transmitted by eating oysters.

Infectious diseases have recently caused some public-health scares. Noroviruses—recently known for causing cruise ship infections—are already on the rise. Cryptosporidium parvum sickened some 400,000 residents of Milwaukee, Wisconsin in 1993, when the local water-treatment process was changed in what had seemed to be a minor way. E. coli O157:H7 is one of the more common infectious noroviruses in the U.S. along with a large number of other dangerous bacteria, many of which are becoming harder and harder to kill with regular antibiotics.

But microorganisms are not the only cause of water-associated illnesses. Chemicals, too, pose serious risks. About a thousand new chemicals are used in the world every year, joining the tens of thousands more that are

already in widespread use. Many eventually end up in the water system. In the United States, for instance, some 700 chemicals have been found in our drinking water sources, and more than a hundred of those chemicals are known to be highly poisonous.

Most people have a good enough immune system to handle a certain amount of water pollutants. But some—infants, the elderly, people living with cancer or AIDS—are more likely to get infected. Elderly adults often sicken on exposure to only a small amount of the infectious dose that would be needed to sicken a healthy person.

DANGEROUS WATERS

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