Carbon dioxide levels may be spiking, but there's one environmental irritant that looks to be partially on the decline: pesticides in our nation's waterways. More stringent regulations and the creation of more Earth-friendly products get some of the credit for this backslide, reports the New York Times, citing a study conducted by the US Geological Survey from 1992 to 2011 and published in the journal Environmental Science & Technology.

Only one stream surpassed a pesticide benchmark for humans in the second decade of the study, down from 17% of agricultural streams from 1992 to 2001.

But while the risk to humans has subsided, aquatic life doesn't get off quite so easy, notes the Times. Up to 61% of agricultural streams and 46% of "mixed-land-use" streams still harbor pesticide levels that surpass acceptable levels for aquatic life; those numbers remained fairly stable over 20 years.

City waterways fared the worst over the study's term: Streams that exceeded the aquatic-life benchmark jumped from 53% in the first 10 years to 90% in the second 10; scientists place much of the blame on a roach and flea killer, as well as a common household insecticide.

Even worse news for aquatic creatures is that the study might not be showing how bad it really is, notes the Times: Because of financial restrictions or insufficient resources, researchers couldn't test for some other commonly used pesticides.

(Read about how a pesticide actually saved Darwin's finches.)

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