Arsenic

TL1
Arsenic Trioxide is the usual toxic form of Arsenic. It's a white powder that acts as an ingested poison (or a respiratory agent if breathed).

Arsenic poisoning can occur accidentally by improperly handling pressure-treated wood, from damp or moldy wallpaper or wall paint that contains arsenic (normally Scheele’s green and Paris green), and from ingesting naturally contaminated well water. Chronic Arsenic poisoning creates characteristic white bands (Mee’s lines) in the fingernails and toenails. The main symptom is severe abdominal pain if ingested, or a cough, runny nose, and laryngitis if inhaled.

As a digestive agent, it has a one-hour delay and a HT-2 roll to resist. Inflicts 1d Toxic damage, repeating hourly for eight cycles. Arsenic Trioxide has no taste. Holdout rolls are at +4; Sleight of Hand rolls are at +2. $1/dose. LC3.

Sources:

Arsenic: GURPS 4th - Basic Set - Combined, page 443 and GURPS 4th - Mysteries, page 36