<Li> Broken sewer lines . </Li> <P> SSOs can cause gastrointestinal illnesses, beach closures and restrictions on fish and shellfish consumption . </P> <P> Developed countries such as the United States, Canada, most Western European nations (e.g. Italy and France), Australia, Singapore, South Korea and Japan are struggling with public health problems of SSO prevention . However, the magnitude of the problem is much greater in most developing countries . </P> <P> The U.S. Environmental Protection Agency (EPA) estimates that at least 23,000 to 75,000 SSO events occur in the United States each year . EPA estimated that upgrading every municipal treatment and collection system to reduce the frequency of overflow events to no more than once every five years would cost about $88 billion as of 2004 . This cost would be in addition to approximately $10 billion already invested . Although the volume of untreated sewage discharged to the environment is less than 0.01 percent of all treated sewage in the United States, the total volume amounts to several billion gallons per annum and accounts for thousands of cases of gastrointestinal illness each year . </P>

Which does not occur as the result of sewage overflows in the united states