UK Guidelines are different in fact they make it clear that copper is essential for health.
"Acute copper toxicity in humans is rare due to the emetic properties and unpleasant taste of the
compounds. There are relatively few data on lower level or chronic oral copper exposure in man.
Copper is kept under tight homeostatic control to prevent the accumulation of excess amounts. Where
dietary copper is high, absorption is reduced and, in particular, biliary excretion increased. Other
mechanisms, which sequester excess copper within the cell, may also occur. Copper toxicity occurs
when such defences are overwhelmed. Thus, in man, liver toxicity has only been seen in genetically
determined conditions such as Wilson’s disease and in Indian Childhood Cirrhosis where hepatic copper
accumulation occurs. There is no evidence for copper carcinogenicity in the general population,
although an elevated incidence of hepatoma has been suggested in untreated Wilson’s disease patients
or subjects recovering from ICC."
Many people confuse the problems of verdigris poisoning with copper poisoning. The use of nickel to coat copper has also caused difficulties and confusion. In fact the UK Food Standards Agency indicate it is safer to use an uncoated copper kettle than an electric kettle with a nickle coated element. There has not been a case of copper toxicity poisoning in the UK or USA recorded in the last 50 years.
Copper is in itself an oxidant, yet in the body it has an antioxidant function by being a participant in the enzyme superoxide dismutase (S.O.D.). This enzyme protects the cells from the damage.
Copper is also part of the protein, ceruloplasmin, found in the blood plasma. Ceruloplasmin regulates the level of certain hormones in the blood and is also required for the formation of red blood cells.
Additionally, copper plays a part in energy production, melanin (Skin pigment) formation and fatty acid oxidation.
The risk of heart and circulatory problems is increased with copper deficiency, especially if accompanied by a deficiency of Selenium.
Copper deficiency can also contribute to Anaemia, some bone diseases and nervous system disorders. In children copper is required for the metabolisation of calcium so a deficiency can be a contributor to growth inhibition and brittle bone disorders.
Copper consumption is actually recommended for Lactating women - normally the group where science gets hyper cautious.
A US Study in 2005 recommended a reduction in the use of copper supplements
in the diet. A minor reduction in the immune system was suggested after 100 days consumption of supplements in excess of 7mg per day. This was contrary to a UK study of 1985 (Pratt) which suggested that the human body maintains homeostasis even with supplementary consumption of 10mg copper per day. (I am not sure about the elevels of copper in US water - here in the UK it is generally less than 1mg per litre with a legal maximum of 3mg - this could explain a discrepancy in the results.)
Copper itself is an algaecide in water and is now used deliberately in water systems to keep it clean and potable. Copper mesh and silver mesh are used together in water purification filters. Recent studies have also shown it has antimicrobial properties and is able to eliminate MRSA, E Coli, Listeria and even Influenza whilst these survive in contact with stainless teel. There have even been recommendations that copper should be used to replace stainless steel operating tables etc.
The UK daily maximum intake guidelines are 16mg per day which could be provided by drinking 8 litres of tea produced in a copper kettle with UK tap water from an acidic area. Of course if you want to eat a kilogram of oysters in the same day I would recommend you reduce your tea intake to four and a half litres or 36 cup fulls just to be on the safe side.
The FSA is at pains to point out that this is a guideline and there is little evidence that exceding these amounts would be hazardous.
There are numerous other studies from all over the World. The EU and WHO guidelines concern themselves with copper supplements and suggest that people should concentrate on trying to glean copper from their diet and drinking water.
Hope that is helpful.