Copper, iron, manganese, strontium, and zinc content of market milk

Samples of market milk collected in alternate months from February 1967 to February 1968 from cities in the United States were analyzed for copper, iron, manganese, strontium, and zinc by atomic absorption spectrophotometry. Ranges and national averages for trace elements in milk, expressed as milligrams per liter, varied as follows: Cu, .044 to .190 and .086; Fe, .20 to 1.51 and .64; Mn, .033 to .211 and .091; Sr, .040 to .480 and .171; and Zn, 2.30 to 5.10 and 3.28. Statistically, the data showed significant differences among months and locations. Trace element contents in milk from the east were significantly different from those in the west; however, means or per cent differences between areas (except for Sr) were less than 10%. Strontium in milk from the west was higher than that from the east. Strontium means were greater than .200 mg per liter in Arizona, California, Colorado, Kansas, Nevada, New Mexico, South Dakota, Utah, and Wyoming. Monthly means for all trace elements showed that Zn was constant throughout the year, whereas other elements were lowest in summer and highest in winter.