The current wiki page on this is not too bad. It seems that farmers that have been using glyphosate heavily are seeing worse and worse results as weeds become more roundup tolerant. Enter 2,4-Dichlorophenoxyacetic acid (it's been somewhat heavily used since 2013).

Mechanism of action is that it mimics a plant growth hormone. Definitely not healthy in larger doses, though short term acute toxity levels require quite a bit of this. At more trace doses, I'm not sure if there is a cancer link or how much; vague classification is that it's a possible carcinogen, though not sure what doses this would need. Personally, glyphate sounds far worse to me.

Men who work with 2,4-D are at risk for abnormally shaped sperm and thus fertility problems; the risk depends on the amount and duration of exposure and other personal factors.

Cancer risk

The International Agency for Research on Cancer classifies 2,4-D as a possible carcinogen to humans while the United States Environmental Protection Agency does not. The International Agency for Research on Cancer (IARC), said 2,4-D was classified as "possibly carcinogenic to humans (Group 2B), based on inadequate evidence in humans and limited evidence in experimental animals".

In June 2015 the World Health Organization's International Agency for Research on Cancer confirmed its 1987 classification of 2,4-D as a possible carcinogen.