Determination of trace elements in human hair. Reference intervals for 28 elements in nonoccupationally exposed adults in the US and effects of hair treatments.

The concentrations of 28 elements in hair of three populations of non-occupationally exposed adults in the US (n = 271) were determined. The 10th, 50th, and 90th percentiles, and geometric means for these data were obtained to define reference intervals for these elements. The effects of various hair treatments, age, and sex on concentrations of 17 selected elements in hair were determined for these populations. Age had little effect on elemental concentrations. Males tended to have higher Cd and Pb levels, but lower Mg and Ti levels than females. Males using dandruff shampoo had significantly higher concentrations of Na, Se, and Ti than those using only regular shampoo and/or conditioners. Ba, Ca, Cu, Mg, Na, and Sr were all elevated in females using permanents or color treatments, compared to those using only dandruff shampoo, regular shampoo, and/or conditioners.

Comparison of an inductively coupled plasma-atomic emission spectrometry method for the determination of calcium, magnesium, sodium, potassium, copper and zinc with atomic absorption spectroscopy and flame photometry methods.

Serum calcium, magnesium, copper and zinc concentrations obtained from the analysis of 77 serum samples by inductively coupled plasma-atomic emission spectrometry (ICP-AES) are compared with the results obtained using atomic absorption spectroscopy (AAS). Similarly, serum sodium and potassium levels from the analysis of the same samples by ICP-AES are compared with the levels obtained by flame photometry. For each metal, we compare the results from both methods with a linear regression program that assumes error in both variables. The regression analysis shows that the ICP-AES method gives slightly higher calcium, copper, and zinc results and lower magnesium results than the AAS methods, and lower sodium and potassium results than the flame photometry method. Except for sodium, the correlation (r) between the results is very high (greater than or equal to 0.958), indicating that the ICP-AES results could be corrected to be equivalent to the atomic absorption or flame photometry results. The ICP-AES has the advantage of requiring less preparation and analysis time, and additional elements could be determined simultaneously in the same sample.

Purification of prealbumin from human serum.

A method is presented by which prealbumin (thyroxine-binding prealbumin; tryptophan-rich prealbumin) may be purified to homogeneity from human serum. The method involves precipitation of contaminating proteins with dilute aqueous phenol, ion-exchange chromatography on DEAE-Sephacel, and gel permeation chromatography on Sephadex G-100. The yield is 25-30%, and the prealbumin is homogeneous by polyacrylamide gel electrophoresis at pH 8.9 and pH 3.6.

Loss of vitamin A in long-term stored, frozen sera.

Vitamin A (retinol) was measured by a high performance liquid chromatography (HPLC) method in human serum samples stored frozen at -20 degrees C for 2-6 yr. In 40% of the sample, both vitamin A and the internal standard, vitamin A acetate (retinyl acetate) which was added at the time of assay, were destroyed. Controlled studies of each phase of the assay showed that the vitamin A began to degrade during the extraction step immediately after ethanol was added to the serum. Vitamin E (alpha-tocopherol) and beta-carotene also degraded concurrently with vitamin A. Vitamin A may be lost because of free radical oxidation after the vitamin is released from its serum binding protein (retinol-binding protein), following the addition of ethanol to the serum sample. The loss of vitamin A is eliminated completely if ascorbic acid (0.1% w/v) is added to the ethanol before it is used in the preassay extraction.

Assessment of 2,3,7,8-tetrachlorodibenzo-p-dioxin exposure using a modified D-glucaric acid assay.

An enzyme-inhibition assay was evaluated and modified to quantify D-glucaric acid in a population exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD). The modified assay combined improvements described separately in previous reports, including pH adjustment by standard addition of buffers rather than by titration, an optimum pH of 2.3 for converting D-glucaric acid to 1,4-glucarolactone, and the use of the relation reciprocal of absorbance versus concentration for calculating unknowns. Reference limits for adult males were 0.06-5.90 mmol D-glucaric acid/mol creatinine and for adult females 0.87-6.23 mmol D-glucaric acid/mol creatinine. Children under the age of 15 yr had a reference range of 0-8.34 mmol D-glucaric acid/mol creatinine. Persons on anticonvulsant therapy excreted from 3 to 10 times the upper reference limits of D-glucaric acid. Urinary concentrations of D-glucaric acid in persons identified as being at high risk for exposure to 2,3,7,8-TCDD in Times Beach, Mo., were not significantly different from concentrations in those identified as being at low risk for such exposure.

Beta-carotene determined in serum by liquid chromatography with an internal standard.

We describe a procedure for quantitative determination of beta-carotene in human serum. The 0.1-mL serum sample is precipitated with ethanol containing the internal standard, dimethyl-beta-carotene, then extracted with hexane. This extract is injected onto a reversed-phase, "high-performance" liquid-chromatography column, and the carotenes are resolved and eluted with an acetonitrile/methylene chloride isocratic solvent system. They are quantified from the peak-height ratios of their absorbance at 450 nm. About 14 min is required for each chromatogram. The procedure has excellent precision and is appropriate for routine use in analysis of large numbers of samples. The method should be particularly useful for clinical studies on the relationship of serum beta-carotene and cancer incidence in human populations.

Chronological trend in blood lead levels between 1976 and 1980.

Analysis of a chronological trend in data from the second National Health and Nutrition Examination Survey indicated that average blood lead levels in the United States dropped approximately 37 per cent (5.4 micrograms per deciliter) from February 1976 through February 1980. There was no evidence that this trend was due to errors in laboratory measurement or to the design of the survey. The trend was present even after accounting for differences in race, sex, age, region of the country, season, income, and degree of urbanization. Changes in exposure to lead in paint or in the diet are unlikely explanations of the trend. However, the correlation of blood lead levels with the lead level in gasoline was highly significant (P less than 0.001) overall and in population subgroups defined by race, sex, and age. Although strong correlation does not prove cause and effect, the most likely explanation for the fall in blood lead levels is a reduction in the lead content of gasoline during this period.