Assessment of Changes in Levels of Mercury, Lead, Cadmium, and Arsenic in Raw Milks during Milk Powder Production

Contamination of milk and its products with heavy metals cause toxic and adverse effects on human health, especially in children. Therefore, the assessment of milk and its other products for the presence of these metals should be highly considered. Therefore, the present study was carried out to assess changes in the levels of mercury, lead, cadmium, and arsenic in raw milk samples during processes of milk powder production.

A total of 50 raw milk, skim milk, and cream samples from a dairy plant in Chaharmahal and Bakhtiari Province, Iran, were assessed. These samples were collected in summers and winters, 2019–2020. Samples were analyzed to investigate their lead, mercury, cadmium, and arsenic using the elemental coupled plasma-optical emission spectroscopy method.

Results showed that the residual quantities of heavy metals in various samples varied; hence, metals such as mercury and lead were more concentrated in the cream phase but cadmium and arsenic metals were more concentrated in skim milk (p < 0.05). Furthermore, residual quantities of all heavy metals in milk powder were much higher than those in cream and skim milk (p < 0.05). Based on the results of this study, international standards (Codex), and Iranian national standards, the average quantities of lead in all products were higher than those of standard levels (20 ppb). Quantities of cadmium in skim milk in the cold season and in condensed milk and milk powder in the two seasons were higher than the standard limits (10 ppb).

Based on the results of the present study, quantities of mercury, cadmium, and especially lead in dry milk are higher than the limit set by the Codex, which can be a potential risk for children consuming milk. Therefore, it is necessary to regularly monitor potential sources of contamination in raw milk and its products.