Angela observes that children from poor families tend to have higher rates of lead poisoning, but she doesn't know if being poor makes people more likely to be exposed to lead, or if people who already have high levels of lead in their bodies are more likely to become poor. Which of the following characterizes what Angela knows about the relationship between poverty and lead poisoning?
1) There is a correlation between poverty and lead poisoning.
2) Any claim that there is a relationship between lead poisoning and poverty is wrong.
3) As poverty is a social condition and lead is a physical element, the relationship between the two cannot be statistically significant.
4) There is a causal relationship between lead poisoning and poverty.