Identify a major risk factor for lead exposure in housing.

Lead-based paint and plumbing fixtures are significant risk factors for lead exposure in housing due to their historical use. In homes built before the late 1970s, lead-based paint was commonly used for its durability and color retention. When this paint deteriorates, especially in areas like windows and doors where it may chip or generate dust, it can pose serious health risks, particularly to young children who are more vulnerable to lead poisoning. Similarly, older plumbing systems often contain lead solder and fixtures, which can leach lead into drinking water, further exacerbating the risk of exposure.

Modern paint formulations, while they may contain other chemicals, typically do not include lead, thus posing less risk. Newly installed roofing materials and retrofitted electrical systems likewise do not directly relate to lead exposure as they are not typically associated with lead content, especially if they adhere to current building codes and safety regulations. This context reinforces why lead-based paint and plumbing fixtures are of primary concern for lead exposure in housing settings.