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Nickel (Ni)
Urinary excretion
of nickel bound to cysteinyl or thiol compounds (such as
glutathione) or to amino acids (histidine, aspartic acid, arginine)
is the predominant mode of excretion. With the exception of specific
occupational exposures, most absorbed nickel comes from food or
drink, and intakes can vary by factors exceeding 100 depending upon
geographical location, food type, and water supply.
Depending upon chemical form and physiological factors, from
1 to 10% of dietary nickel may be absorbed from the gastrointestinal
tract into the blood. Urine reflects recent exposure to nickel and
may vary widely in nickel content from day to day due to the above
factors. Sources of
nickel are numerous and include the following.
. Cigarettes (2 to
6 mcg Nickel per average cigarette)
. Diesel exhaust
(particulates may contain up to 10 mg/gram Nickel)
. Foods,
especially: cocoa, chocolate, soya products, nuts, and hydrogenated
oils
. Nickel-cadmium
batteries
. Nonprecious,
semiprecious dental materials
. Nickel-containing
prostheses
. Electroplating,
plated objects, costume jewelry
. Pigments (usually
for ceramics or glass)
. Catalyst
materials (for hydrogenation processes in the food, petroleum and
petrochemical industries)
. Arc welding
. Nickel refining
and metallurgical processes
Most clinically
observed nickel contaminations are manifested as dermatoses –
contact dermatitis and atopic dermatitis. However, Nickel
hypersensitizes the immune system causing hyperallergenic responses
to many different substances. Because Nickel can displace zinc from
binding sites on enzymes, it can have inhibiting or activating
effects on such enzymes. Nickel sensitivity is observed to be three
to five times more frequent in women than in men.
Other laboratory tests or clinical findings that would be
indicative of Nickel excess are; hair element analysis, presentation
of multiple allergic sensitivities, dermatitis, positive patch test
for ”Ni allergy”, proteinuria, hyperaminoaciduria (by 24-hour urine
amino acid analysis). Detoxification treatments with administration
of EDTA or sulfhydryl agents (DMPS, DMSA, D-penicillamine) may
increase urine nickel levels depending upon: body burden and
mobility in tissues, duration of treatment, dosage and other
factors.