If most tap water in the U.S. is safe to drink, why are engineers and scientists still doing so much research on drinking water, and why is the federal government thinking about more regulations?

Good question. It would be easy to assume that because your drinking water is safe, or your car...that it's ok to not mess with perfection. Sounds logical, right? The problem is the knowledge base about what treatment methods make your water safe, or what new organisms may make it unsafe, is always changing.

In short, science is always finding a better way to make better water, or safer cars for that matter.

In truth, there is no such thing as perfection when it comes to water treatment. Water that meets all of the federal and state regulations is considered safe to drink, but it is not completely risk-free. Risk-free tap water would be very expensive, so in setting standards, the government chooses an acceptable risk (very small). Public consumers want to keep lowering this risk even further while not spending much money. This is one of the goals of research and new government regulations. Many secondary standards provide the groundwork for the future regulations.

What are Secondary Standards? The U.S. Environmental Protection Agency (EPA) has established National Primary Drinking Water Regulations that set mandatory water quality standards for drinking water contaminants. These are enforceable standards called "maximum contaminant levels" or "MCLs", which are established to protect the public against consumption of drinking water contaminants that present a risk to human health. An MCL is the maximum allowable amount of a contaminant in drinking water which is delivered to the consumer . In addition, EPA has established National Secondary Drinking Water Regulations that set non-mandatory water quality standards for 15 contaminants. EPA does not enforce these "secondary maximum contaminant levels" or "SMCLs." They are established only as guidelines to assist public water systems in managing their drinking water for aesthetic considerations, such as taste, color and odor. These contaminants are not considered to present a risk to human health at the SMCL.

Why Set Secondary Standards? Since these contaminants are not health threatening at the SMCL, and public water systems only need test for them on a voluntary basis, then why it is necessary to set secondary standards? EPA believes that if these contaminants are present in your water at levels above these standards, the contaminants may cause the water to appear cloudy or colored, or to taste or smell bad. This may cause a great number of people to stop using water from their public water system even though the water is actually safe to drink. Secondary standards are set to give public water systems some guidance on removing these chemicals to levels that are below what most people will find to be noticeable.

As researchers gain more knowledge and discover new potential problems, new regulations are needed to eliminate or reduce the risks associated with these problems. Additional research resulted in the arsenic standard being changed from 50 to 10 parts per billion in 2001. Research will continue to provide new insights into setting higher and more stringent standards on the path to a higher quality drinking water.