The World Health Organization (WHO) has raised a flag on another agricultural chemical.

The WHO's International Agency For Research on Cancer (IARC) has classified the weed killer 2,4-D as "possibly" causing cancer to humans.

2,4-D is one of the active ingredients used in Dow AgroSciences herbicide Enlist Duo. The product also contains glyphosate, which the WHO earlier this year deemed as "probably" carcinogenic.

Dow AgroSciences responded by saying that the classification of 2,4-D as possibly causing cancer is inconsistent with government findings in nearly 100 countries, including the US and Canada, which have for decades affirmed the safety of the chemical when used according to approved labelling.

"No herbicide has been more thoroughly studied and no national regulatory body in the world considers 2,4-D a carcinogen," said John Cuffe, Global Regulatory Sciences and Regulatory Affairs Leader, Dow AgroSciences.

For 70 years, 2,4-D has been widely used around the world to help protect crops, pastures and other areas from noxious and invasive weeds.