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A process called risk assessment is used to set drinking water quality standards. When assessing the cancer and non-cancer risks from exposure to a chemical in drinking water, the first step is to measure how much of the chemical could be in the water. Next, scientists estimate how much of the chemical the average person is likely to drink. This amount is called the exposure.
Risks are estimated separately for cancer and non-cancer effects. For cancer effects, a risk assessment estimates a measure of the chances that someone may get cancer because they have been exposed to a drinking water contaminant. EPA generally sets maximum contaminant levels MCLs at levels that will limit individuals risk of cancer from that contaminant to between 1 in 10,000 and 1 in 1,000,000 over a lifetime. For non-cancer effects, the risk assessment estimates an exposure level below which no adverse effects are expected to occur. The EPA has considered Point of Entry (POE) and Point of Use (POU) as a viable treatment technology for small communities with less than 1000 people but will only allow them to be used by a treatment utility NOT by the individual homeowner. This will make certain that there is accountability for the service of the equipment. The EPA has also required pre-oxidation in single house or single treatment situations. This means that if you have your own well system and you plan on using reverse osmosis or any other of the above technologies you must first use chlorine to oxidize your well water. This will convert any As-III species of arsenic to As-V so that it is more readily removed by your treatment options. Community water systems that serve large populations of people that will be over the new standard of 5 ppb will need to start being retrofited with the necessary equipment to keep the system within the new 5 ppm standard. Treatment for arsenic is readily available to community water treatment systems. The treatment technologies that have been considered by the EPA as viable methods of treatment for bringing arsenic levels to below the new 5 ppb standard are as follows
In no particular order of effectiveness As development in our modern society increases, there are a growing number of threats that could contaminate our drinking water. Suburban sprawl has encroached upon once-pristine watersheds, bringing with it all of the by-products of our modern life style. Actual events of serious drinking water contamination occur seldom in this country, although in the country Bangladesh high levels of Arsenic in numerous shallow and deep wells in various parts of the country has raised serious health concerns.
Recent investigations, though incomplete, confirm that the occurrence of Arsenic in groundwater is more widespread than assumed at first and that it already
affects a large number of people. The latest statistics available on arsenic contamination in the groundwater indicates that 59 districts around 85% of the total area of Bangladesh and about 75 million people are at risk. It is estimated that at least 1.2 million people are exposed to Arsenic poisoning and 24 million potentially exposed. With the threats of such events increasing, we cannot take drinking water safety for granted. Greater vigilance by you, your water supplier, and your government is vital to ensure that such events do not occur in your water supply.
 David Walling  "Plumbers Protect The Health Of The World." 
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In developing drinking water standards, EPA assumes that the average adult drinks 2 liters of water each day throughout a 70-year life span.| David Walling - [Qualifications] | [Email] | [Website] | [Articles] |
| The views expressed in this article are those of the individual author and do not necessarily reflect the views of the management or staff of MasterPlumbers.com |
