Testing marijuana for pesticides: How we did it

In March, two reporters for The Oregonian/OregonLive bought 10 extracts from three recreational marijuana stores in Portland. The following month, we bought an additional five extracts from three more stores.

Why extracts? Sold as oils or solids known as wax and shatter, extracts are susceptible to contamination because pesticides tend to concentrate during production.

Source: Testing marijuana for pesticides: How we did it | OregonLive.com