The researchers studied how earthworms absorb and eliminate harmful chemicals called polycyclic aromatic hydrocarbons (PAHs) in soil. They found that the earthworms reached a peak in PAH levels in their bodies around day 7, likely due to a decrease in the chemicals in the soil water that the earthworms can absorb. The rate at which earthworms take in PAHs is similar for all types, but the rate at which they eliminate them decreases with the chemical's properties. Overall, the earthworms' ability to accumulate PAHs aligns well with how these chemicals move between soil water and the earthworms' bodies.