By the 1960s, DDT had contaminated water, soil, plants, and animals and threatened the future survival of many living things.
(DDT; had contaminated; water, soil, plants, and animals; T:By the 1960s) (DDT; threatened; the future survival of many living things; T:By the 1960s)
DDT DDT
had contaminated threatened
water, soil, plants, and animals T:By the 1960s
the future survival of many living things T:By the 1960s