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.
More than 4 percent of children in the United States have lead poisoning. Rates of lead poisoning are even higher in large cities and among people with low incomes. The most common cause of lead poisoning today is old paint with lead in it. Lead has not been used in house paint since 1978. However, many older houses and apartment buildings (especially those built before 1960) have lead-based paint on their walls. Toddlers explore their world by putting things in their mouths.