What is a leachate? Why is it harmful for soil and water?

Leachate is formed when rain water leaks into the landfill. As the water percolates through the landfill, chemical processes turn it acidic. This acidic water then dissolves toxic chemicals from common hazardous waste products such as household cleaners, insect sprays and paints. This resulting toxic leachate leaks through the bottom and sides of the landfill and contaminates water and soil.