Plasma, dietary value

Since about 90% of plasma copper is bound to ceruloplasmin, factors that increase the hepatic synthesis of ceruloplasmin, such as an APR or the oral contraceptive pill, will increase plasma copper independently of dietary copper intake. In premature infants with fiver immaturity and low ceruloplasmin synthesis, plasma copper values below 30 IXg/L (<5pmol Cu per L) suggest the necessity for increased copper input. 

An additional difficulty in defining normal plasma lipid values results from the influence of various factors on plasma lipid concentrations. Cholesterol and phospholipid concentrations vary with age and show an increase from the third to the sixth decade followed by a slight decrease thereafter (Adlersberg et al. 1956, Lewis et al. 1957, Schaefer et al. 1958). In higher decades values may be influenced by the inclusion of persons with clinically silent disease. Furthermore, alimentary influences result from the total amount of ingested fat and the composition of dietary fatty acids. Therefore, blood samples should not only be taken in the fasting state, but in many instances after a period of controlled dietary intake. 

Based on the data from controlled human studies, the NOEL for plasma cholinesterase inhibition for a single dose of chlorpyrifos is between 0.1 and 0.5 mg/kg bw/day, and the more conservative 0.1 mg/kg bw/day (100 pg/kg bw/day) is used in this assessment as the acute NOEL for chlorpyrifos. The repeated dose NOEL in humans is 0.03 mg/kg bw/day (30 pg/kg bw/day), based on plasma cholinesterase activity, and this is the basis for the establishment of the reference dose of 0.003 mg/kg bw/day (3 pg/kg bw/day) used by the EPA in assessing dietary risk to chlorpyrifos. For the work described here, both NOELs are used as bases for assessing risks to persons who have the potential for non-dietary exposure to chlorpyrifos. For exposures that are infrequent or of short duration, the 100 pg/kg bw/day NOEL is assumed to be the more appropriate value, and the lower 30 pg/kg bw/day will be used in those situations in which exposure may be considered to be more frequent. ... 

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