The safe amount of lead exposure is essentially zero, as no level of lead in the blood or environment is considered completely safe. For children, the Centers for Disease Control and Prevention (CDC) has lowered the blood lead reference value to 3.5 micrograms per deciliter (µg/dL) to better detect elevated levels, highlighting that even this low level can be harmful. For adults, the CDC and the National Institute for Occupational Safety and Health (NIOSH) consider a blood lead level of 5 µg/dL or higher elevated, and symptoms of lead poisoning can occur at blood lead levels as low as 25 µg/dL. Occupational exposure limits in air are set at 0.15 mg/m^3, and blood lead suspension levels considered concerning are 60 µg/dL for men and 30 µg/dL for women, with risks observed at levels around 40 µg/dL. Lead exposure can affect the nervous system, kidneys, blood (causing anemia), and reproductive function. In terms of dietary intake, the FDA has interim reference levels aimed at minimizing toxicity: 2.2 micrograms per day for children, 8.8 micrograms per day for women of childbearing age, and this latter threshold is also advised for all adults. The Environmental Protection Agency (EPA) has set the maximum contaminant level goal for lead in drinking water at zero, acknowledging there is no safe level of lead exposure. Overall, the guiding principle is to minimize lead exposure as much as possible due to its toxicity and cumulative harm risk; even very low levels of lead in blood or environment can be harmful, especially to children and pregnant women. Regular monitoring and mitigation are critical where lead exposure is a concern.