What lead actually does, system by system

Before you click into the pages below, here's the plain version. Lead gets into the bloodstream and then it goes everywhere blood goes, so it doesn't really pick one target. But some systems take the worst of it.

Brain and nervous system. This is the big one, especially in kids. A developing brain is still building the connections that handle attention, impulse control, and learning, and lead interferes with that wiring. There's no threshold where it stops mattering. Studies going back decades, and reaffirmed by CDC and the CDC's Advisory Committee on Childhood Lead Poisoning Prevention, show blood lead levels well below what used to be considered "acceptable" are still linked to lower measured IQ and higher rates of attention and behavior problems. In adults the nervous system effects are subtler, things like slower reaction time and, with very high or long-term exposure, peripheral nerve damage.

Blood. Lead interferes directly with heme synthesis, the process that builds the oxygen-carrying part of red blood cells. It blocks a couple of the enzymes in that pathway. The practical result is anemia, and it's actually one of the oldest documented effects of lead poisoning, recognized clinically for well over a century.

Kidneys. The kidneys filter lead out of the blood, and with enough exposure over enough time, that filtering work damages the kidney tissue itself. Long-term lead exposure is associated with reduced kidney function and, in occupational and heavy-exposure populations, chronic kidney disease.

Bones. This is the part most people never hear about. Somewhere around 90 percent of the lead in an adult's body ends up stored in bone, chemically parked there because it behaves a lot like calcium. It can sit there for decades. The catch is that bone is not a permanent vault, it remodels constantly, and calcium (with the lead riding along) gets released back into the bloodstream. This matters most during pregnancy and breastfeeding, when a mother's bones are actively releasing calcium to support the baby, and any lead stored from exposure years or even decades earlier can come back out and cross to the fetus.

Cardiovascular system. In adults, chronic low-level lead exposure is linked to higher blood pressure, and at a population level to more heart disease and stroke. It's not a dramatic effect at typical exposure levels, more of a steady upward push on cardiovascular risk over a lifetime.

Reproductive system. Lead is associated with reduced fertility in both men and women, and with pregnancy complications including higher miscarriage risk and lower birth weight. Combined with the bone storage issue above, this is part of why lead exposure earlier in life keeps mattering for reproductive health years later.