An effort to disinfect the water in the D.C. area may have contaminated as many as 15,000 homes. The disinfectant caused corrosion in lead pipes that leached into the water supply. The CDC has concluded that many homes may still be at risk of elevated levels of lead contamination.
For more information you can find the full report here.
Many older homes may still use lead pipes for the water supply and this can increase the risk of lead contamination. In some cases the visible piping in the home may be made of PVC or copper, but the service lines that lead to the house may be lead. Here are some tips to check if your house has lead water lines from ehow.
You can also test your own water for lead contamination with a Drinking Water Test for Lead.
If you know that you have lead pipes or that you are at risk of lead contamination you can also use a water filter to remove lead from drinking water. Just make sure that the filter cartridge you are using is NSF certified for lead reduction. A simple inline filter like the GXRLQ from GE reduces 99% of lead as well as filtering out chlorine, cysts, asbestos and other contaminants.