Hi Mohammed, you can only derive a protein concentration from a competitive ELISA under very special circumstances. If you are not sure whether you have these conditions in your experiment you should work with IC50 values.
About Lead-Based Paint. Lead is a highly toxic metal that may cause a range of health problems, especially in young children. When lead is absorbed into the body, it can cause damage to the brain and other vital organs, like the kidneys, nerves and blood. Lead may also cause behavioral problems, learning disabilities, seizures and in extreme cases, death.
Both adults and children get lead poisoning from exposure to lead in their environment. However, the causes of that exposure are typically different. For example, one of the biggest sources of lead exposure in children is paint with lead in it because small children may eat peeling paint or chew on a painted surface.