IPCS concluded that the upper limit of the acceptable range of oral intake in adults
is uncertain but is most likely in the range of several (more than 2 or 3) but not many
milligrams per day in adults. This evaluation was based solely on studies of gastrointestinal
effects of copper-contaminated drinking-water. The available data on toxicity
in animals were not considered helpful in establishing the upper limit of the acceptable
range of oral intake due to uncertainty about an appropriate model for humans,
but they help to establish a mode of action for the response. The data on the gastrointestinal
effects of copper must be used with caution, since the effects observed
are influenced by the concentration of ingested copper to a greater extent than the
total mass or dose ingested in a 24-h period. Recent studies have delineated the threshold
for the effects of copper in drinking-water on the gastrointestinal tract, but there
is still some uncertainty regarding the long-term effects of copper on sensitive populations,
such as carriers of the gene for Wilson disease and other metabolic disorders
of copper homeostasis