Final answer:
The nurse should focus on assessing the Central nervous system for irreversible effects of lead poisoning in a toddler living in an old building, as lead exposure can cause significant developmental and cognitive issues.
Step-by-step explanation:
In a toddler living in a very old building, a nurse should carefully assess the child for the irreversible effects of possible lead poisoning by focusing on the Central nervous system (CNS). Exposure to lead can cause developmental delays, lower IQ, hyperactivity, behavior and learning problems, slowed growth, hearing problems, anemia, and more severe outcomes like seizures, coma, or even death at high exposure levels. The CNS is particularly vulnerable, as lead exposure can lead to lifelong effects including learning disabilities, behavioral issues, and reduced cognitive function. These impacts of lead are often irreversible, though certain therapies may help a child to manage the effects more effectively. It is also crucial for families to take steps to prevent further exposure by maintaining a clean home environment and ensuring a nutritious diet for the child to help minimize lead absorption.