Toxic concentration

In acute arsenic poisoning, urinary arsenic concentration is the best indicator of recent exposure. A urinary arsenic concentration above 1000 micrograms/L in a 24-hour urine collection indicates acute arsenic poisoning. Raised urinary arsenic concentration in a spot urine collection can also indicate recent exposure. However, urinary arsenic concentrations are rarely available in a timely manner and most treatment for acute arsenic poisoning is started empirically. Blood arsenic concentrations are rarely available.

Fish, shellfish and organic rice can contain relatively nontoxic organic arsenic compounds. Ingestion can cause a raised urinary arsenic concentration for up to 2 weeks, or even longer if it was a large ingestion. Routine arsenic assays do not differentiate between toxic inorganic and less toxic organic forms.