Metals in Cow Milk and Soy Beverages: Is There a Concern?

Overview

Andrade and colleagues measured lead, cadmium, and manganese in 28 retail beverages purchased on the Portuguese market in Lisbon between February and May 2019, split evenly between 14 cow-milk (CM) brands and 14 soy-beverage (SB) brands. The basis is liquid as-purchased, measured in micrograms per liter; the authors do not convert to per-kilogram or apply a reconstitution factor. Soy beverages carried significantly higher cadmium (mean 5.6 μg/L vs 2.15 μg/L, p < 0.05) and roughly twenty-fold higher manganese (mean 117.4 μg/L vs 5.93 μg/L, p < 0.05) than cow milk; lead was numerically higher in cow milk (19.3 vs 13.4 μg/L) but the difference was not statistically significant (p > 0.05). The cow-milk lead (Pb) mean sat just under the EU 2023/915 maximum level of 20 μg/kg, and one cow-milk brand’s cadmium value exceeded the 5 μg/kg EU ceiling that applies to infant-formula products manufactured from cow’s milk proteins.

Key numbers

All concentrations below are in micrograms per liter (μg/L) of the beverage as purchased and as analyzed. The authors did not apply density conversion to express values per kilogram in the results tables; they cite a cow-milk density of 1.030 kg/L when comparing their lead value to the EU 20 μg/kg ceiling.

Global means by beverage class

Within-class ranges across brands

Within the 14 cow-milk brands, lead ranged from 5.6 to 39.9 μg/L, cadmium from 0.6 to 6.8 μg/L, and manganese from 4.6 to 8.9 μg/L. Within the 14 soy-beverage brands, lead ranged from 5.4 to 41.7 μg/L, cadmium from 0.9 to 15.4 μg/L, and manganese from 72.3 to 177.9 μg/L. Per-brand values are reported in Tables 10 and 11 of the source under anonymized codes CM1-CM14 and SB1-SB14; this page does not reproduce the per-brand table under the brand-firewall rule.

Regulatory benchmarks the authors cite

The Commission Regulation (EU) 2023/915 maximum level for lead in milk is 0.020 mg/kg, or 20 μg/kg. Converting the cow-milk lead mean of 19.3 μg/L using the cited density of 1.030 kg/L gives roughly 18.7 μg/kg, close to but below the ceiling. The same regulation sets a 5 μg/kg ceiling on cadmium in infant formula, follow-on formula, foods for special medical purposes intended for infants and young children, and formulas for young children placed on the market in liquid form and manufactured from cow’s milk proteins or cow’s milk protein hydrolysates. The mean cow-milk cadmium of 2.15 μg/L falls below that 5 μg/kg ceiling, but one cow-milk brand reached 6.8 μg/L of cadmium, which is above the 5 μg/kg ceiling that would apply if that milk were used as the cow’s-milk protein source in a liquid infant formula. The paper notes that European legislation has not set maximum levels for the metals studied here in soy beverages specifically.

Method validation

Calibration coefficients of determination ranged from 0.995 to 0.999 across the three metals. Limits of detection by the calibration-plot method were 0.767 μg/L for Pb, 0.294 μg/L for cadmium (Cd), and 1.375 μg/L for Mn; limits of quantification were 2.325 μg/L for Pb, 0.892 μg/L for Cd, and 4.166 μg/L for Mn. Intra-day precision relative standard deviation ranged from 2.63 percent for lead to 5.80 percent for cadmium. Accuracy was assessed against certified reference material NRCC TM-24.3 (fortified lake water) and yielded Z-scores below 2 for all three metals (Pb 1.47, Cd 0.68, Mn 1.47), which the authors take as evidence that the method is valid given the absence of a milk-matrix or soy-beverage-matrix CRM.

Context against other published cow-milk lead values

The discussion places the Portuguese cow-milk lead mean (19.3 μg/L) into context against prior surveys: Solis et al. 2009 reported 65 μg/L in Mexico, Amer et al. 2021 reported 45.06 μg/L in Egypt, Derakhshesh and Rahimi 2012 reported 13.45 μg/L in Iran, Oliveira et al. 2017 reported 2.12 to 37.36 μg/L in Brazil, Zhou et al. 2019 reported 0.46 to 2.96 μg/L in China, and Freschi et al. 2011 reported values below an unspecified limit of detection (1.49 μg/L) in Brazil. The Portuguese mean sits in the middle of this distribution.

Methods (brief)

Sample preparation digested 0.5 mL of beverage (CM or SB) in a polytetrafluoroethylene (PTFE-Teflon) digestion vessel with 6 mL of 2N nitric acid and 1 mL of 30 percent hydrogen peroxide; the mixture stood at room temperature for three hours with the vessels closed, then proceeded through a five-step microwave digestion program in a Berghof Speedwave Two apparatus reaching 170-200 °C at 90 percent power. Vessels cooled overnight, were transferred to a 15 mL volumetric flask with three ultrapure-water rinses, and were brought to volume before analysis. Quantification used a PerkinElmer AAnalyst 700 graphite furnace atomic absorption spectrometer with deuterium background correction and single-element hollow-cathode lamps. Magnesium nitrate at 2 g/L was used as a chemical modifier for manganese; no modifier was added for cadmium or lead because the authors found it had no effective benefit. Selected wavelengths were 228.8 nm (Cd), 279.5 nm (Mn), and 283.3 nm (Pb). Statistical comparison between CM and SB groups used the Mann-Whitney U test after the Kolmogorov-Smirnov test rejected normality, with significance set at p < 0.05.

Implications

Certification: This is a Portuguese-retail-market liquid-beverage survey with N = 14 per class, peer-reviewed in Toxics and CRM-validated against TM-24.3. It is direct evidence for cow-milk-as-purchased and soy-beverage-as-purchased lead, cadmium, and manganese occurrence on a single EU national market in 2019. It is not direct evidence for cow-milk-derived infant formula, soy-protein infant formula, or any powdered or reconstituted product; the authors note that European maximum levels for these metals apply to infant formula and similar products manufactured from these milks but did not themselves test such reconstituted products. Pooling these values into clean-or-dirty subcategory percentiles requires recognizing that the basis is liquid as-purchased in μg/L, not as-consumed per kilogram, and that the publication date is recent enough that a 2030-era pool covering 2019-2030 retail sampling can include these rows without geographic-bias concerns specific to outdated literature.

App: Route to cow milk, soy beverage, milk and dairy, plant-milks-soy-based, lead, cadmium, and manganese. The CM mean lead value sitting one μg/L under the EU 20 μg/kg ceiling is a useful retail-market reference for app-level “how close to the regulatory limit” framing for European-market cow milk. Do not route as cow-milk-derived infant formula or soy-protein infant formula evidence; the authors did not test those products.

Courses: Useful for teaching the cow-milk versus plant-based beverage contamination comparison, the manganese-in-soy issue (soy beverages here carried Mn at roughly twenty times cow-milk levels, in line with prior reports that soy as a botanical accumulates Mn from soil and water), the distinction between metals with set EU ceilings in milk-based products (Pb, Cd) and metals without (Mn), and the discipline of comparing a retail-market mean against a regulatory ceiling using an explicit density conversion rather than treating μg/L and μg/kg as interchangeable.

Related evidence

• Milk and Dairy
• Soy Milk
• Milk and Dairy (HMTc Category 24 master)
• Plant Milks, Soy-Based
• Lead
• Cadmium
• Manganese
• Commission Regulation (EU) 2023/915 cadmium maximum levels
• EU Regulation 2023/915 — Lead Maximum Levels for Infant and Young-Child Foods

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