The World Health Organization (WHO) is cracking down on another popular herbicide used in modern farming, calling it "possibly carcinogenic," and raising concerns about its effects on human health.

In March, WHO released a report concluding that glyphosate, the herbicide used in Roundup, is "probably carcinogenic" to humans. And now the agenct has turned its attention to another popular chemical. A new report released this week is raising similar concerns about 2,4-dichlorophenoxyacetic acid, known as 2,4-D citing that it may be "possibly carcinogenic" to humans.

You may have noticed the "possibly" designation which is a step below the "probably" designation given to Roundup. But it's also two steps above the "probably not carcinogenic" ruling that would indicate there are no concerns about its use affecting human health.

The report was issued by WHO's International Agency for Research on Cancer (IARC), a group that lacks regulatory or enforcement muscle, but its reports tend to influence policymakers. The IARC decided upon the "possibly carcinogenic" classification for 2,4-D after reviewing all of the scientific studies and determining that there is "inadequate evidence in humans and limited evidence in experimental animals" when it comes to the link between the herbicide and cancer.

The herbicide 2,4-D was created in 1945 and has since been used to control weeds in farming, forestry and residential settings.

Dow AgroSciences, a unit of The Dow Chemical Co. and the manufacturer of 2,4-D, said in a statement that IARC's classification was flawed and was "inconsistent with government findings in nearly 100 countries" that have claimed that 2,4-D is safe.

But Dana Loomis, a deputy section head for IARC, said the studies in their research indicated — at best — mixed results. Hence the designation.

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