The study looked at soil fertilized with different types of compost made from municipal waste and green waste. They found that composting municipal waste increased the amount of polycyclic aromatic hydrocarbons (PAHs) in the soil compared to green waste compost. The highest levels of PAHs were seen in soil treated with the highest rates of one- and three-month-old municipal waste compost. However, the levels of PAHs in most cases did not exceed natural levels. Green waste compost had similar PAH levels to the control soil.