PEG-9 Tridecyl ether Trideceth-9 as well as in cosmetic products, it is used for the removal of heavy metals such as Cadmium from wastewater (1).

It is considered safe by the CIR expert committee (2).

References_________________________

(1) Removal of trace Cd2+ from aqueous solution by foam fractionation.
Lu J, Li Y, Zhang S, Sun Y.
J Hazard Mater. 2015 Apr 9;286:466-73. doi: 10.1016/j.jhazmat.2015 

(2) CIR EXPERT PANEL MEETING 
DECEMBER 13-14, 2010

(3) Use of polyethylene glycol in functional constipation and fecal impaction.
Mínguez M, López Higueras A, Júdez J.
Rev Esp Enferm Dig. 2016 Nov

Effectiveness of senna vs polyethylene glycol as laxative therapy in children with constipation related to anorectal malformation.
Santos-Jasso KA, Arredondo-García JL, Maza-Vallejos J, Lezama-Del Valle P.
J Pediatr Surg. 2016 Oct