Blood lead level is a test that measures the amount of lead in the blood. This test is used to screen people at risk for lead poisoning. This may include industrial workers and children who live in urban areas. Lead serves no function in the human body. However, most people have a small amount of it in their bodies because it is so prevalent in our surroundings. Lead exposure occurs when lead dust or fumes are inhaled, or when lead is ingested via contaminated hands, food, water, cigarettes or clothing. Causes of environmental contamination include industrial use of lead, such as is found in plants that process lead-acid batteries or produce lead wire or pipes, and metal recycling and foundries. In adults, a low level of lead exposure isn't considered dangerous. However, in babies and young kids whose brains are still developing, even a small amount of lead can cause learning disabilities and behavioral problems. At higher levels, lead exposure can cause seizures, coma, and even death.