Tuesday, October 03, 2006

Chlorine and Potential Concerns to CF


Chlorine occurs naturally as a component of salt. It is a diatomic molecule and is a toxic, non-metallic flammable gas. Because of its high degree of effectiveness in killing harmful microorganisms (e.g. bacteria), chlorine is a widely used chemical for the treatment of public water supplies. The purpose of this report is to present a brief description of how chlorine is used as a disinfectant for water supply. Using information gathered from reputable websites, medical journals and regulatory documentation, it will also describe how chlorine reacts with other compounds to form trihalomethanes and why this is of concern to persons with impaired pulmonary function due to asthma or cystic fibrosis.

The Disinfection Process: Beneficial and Necessary

Clean, safe water is vital to the overall health of every individual. Before water can be fit for human consumption or use, it must undergo a series of physical and chemical processes. The practices of water filtration and treatment vary only slightly depending on whether the end use of the water needs to comply with Federal regulatory requirements of the Safe Drinking Water Act or the Clean Water Act.

The general process for water treatment takes place as follows:

Raw water from surface water (i.e. local rivers or reservoirs) pass through a large screen. This removes the largest debris such as leaves, rocks, trash and sediment from the water. The water then flows toward a treatment tank where it undergoes rapid mixing. This phase is part of what is called "pre-treatment." During pretreatment strong disinfectant chemicals are added to the water. These chemicals are chlorine, ammonia, lime, and aluminum sulfate.

When the chlorine reacts with ammonia, it forms chloramines. These powerful new compounds are able to kill harmful bacteria and viruses. Because chloramines are highly stable and persistent, they are able to continue protecting the water long after it has left the treatment facility. This ensures that the water flowing out of our tap at home is safe to drink and free from bacteria.

The purpose of adding lime is to adjust the pH of the water. pH is a measure of how acidic something is. Water should be of neutral pH. Addition of aluminum sulfate into the disinfected water promotes even distribution of the chemicals that have been added. It also acts as a coagulant, meaning that it causes any other particles that remain in the water to stick together forming a "floc." Because flocs are made up of several particles, they become heavier than the water molecules and sink to the bottom of the mixing tank. Once the flocs have collected, they are removed. Flocs are harmless bits of sediment and can be recycled back into the environment sort of like applying mulch to a garden.

The water then undergoes another round of filtration and another series of treatment with chloramines and lime. Some cities are required to add fluoride to their drinking water supply, and that takes place during this phase of treatment. Another chemical, called orthophosphate is added to protect the pipes that the water will travel through. It works by preventing corrosion which could adversely affect the pH of the water or cause small amounts of metals to be present.

Clean, safe drinking water is then pumped from the treatment facility to consumers.

Chlorine's effects on lung health

Throughout the last decade, as asthma has undergone increased scrutiny by epidemiological researchers, several resources have come to light regarding the hazards associated with chlorine exposure. Chloramines are known to cause an increase in the frequency and severity of bronchospasms/bronchoconstriction associated with asthma and other pulmonary diseases, such as cystic fibrosis. Public drinking water supplies and the disinfection process it undergoes, do not present nearly the same level of concern as do sources like public swimming pools. It is the author's recommendation that areas where chlorine bleach or pool chlorine are used in noticeable amounts (i.e. detected by smell) are to be reasonably avoided by persons with compromised lung function.

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Additional resources


EPA Chlorine Hazard Study

Chlorine in Pools May Cause Breathing Trouble
The Connection Between Chlorine and Asthma
European Investigators Identify Potential Cause of Asthma in Swimmers (Doctor's Guide)
Office of Environmental Health (OEHA) Toxic Air Contaminants
Aqualyse (R) Pool Chlorine Linked to Asthma Epidemic








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