Glyphosate the main ingredient in Roundup is poisonous to humans, wildlife and the environment. According to the WHO it is 'probably carcinogenic'.
https://www.scientificamerican.com/article/widely-used-herbicide-linked-to-cancer/
It is being sprayed on roadsides, paths, in housing estates close to where people live.
Ireland has the second highest levels of glyphosate in surface water in the EU. Page 83
http://onlinelibrary.wiley.com/doi/10.2903/j.efsa.2015.4302/epdf