Tracking Trace Elements Found in Coffee and Infusions of Commercially Available Coffee Products Marketed in Poland

Overview

Pokorska-Niewiada and colleagues measured lead and cadmium in commercially available ground and instant coffees sold in Poland, then measured transfer into brewed coffee infusions. The dry coffee concentrations were low, and the authors reported limited transfer into ground-coffee brews, especially for lead.

Key numbers

The study analyzed instant and ground coffees from eight producers (four ground, four instant), with each assortment represented by five batches and three samples per batch, giving n=60 per coffee type and n=120 total. Coffee infusions were prepared from 6.330 g of ground or instant coffee in 100 mL hot deionized water with a 10-minute brewing time.

Table 2a reports dry coffee concentrations. Ground coffee beans had mean lead (Pb) 0.015 +/- 0.004 ug/g (range 0.009-0.020 ug/g) and cadmium (Cd) 0.017 +/- 0.002 ug/g (range 0.013-0.019 ug/g). Instant coffee had mean Pb 0.014 +/- 0.003 ug/g (range 0.010-0.020 ug/g) and Cd 0.015 +/- 0.002 ug/g (range 0.012-0.019 ug/g).

Table 2b reports transfer from ground coffee into infusion: Pb 7.10 +/- 1.63% and Cd 30.05 +/- 3.27%. Instant coffee was treated as 100% transferred because the dry instant product dissolves in the drink.

Table 2c reports coffee-drink concentrations. Ground-coffee drink had mean Pb 0.007 +/- 0.002 ug/100 mL (range 0.004-0.009 ug/100 mL) and Cd 0.031 +/- 0.003 ug/100 mL (range 0.025-0.035 ug/100 mL). Instant coffee had mean Pb 0.090 +/- 0.016 ug/100 mL (range 0.065-0.126 ug/100 mL) and Cd 0.096 +/- 0.014 ug/100 mL (range 0.078-0.118 ug/100 mL).

The authors’ exposure calculations found low toxic-element intake from coffee brews. Table 5 reports Cd THQ ranges of 0.0004-0.0005 for ground coffee and 0.0011-0.0017 for instant coffee. The abstract states that lead did not exceed 0.9% of the BMDL0.1 and cadmium did not exceed 0.2% of PTMI even under higher-consumption assumptions.

Methods (brief)

The authors digested 0.500 g coffee samples with nitric acid by microwave-assisted mineralization. Infusions were mineralized from 10 mL aliquots after brewing and cooling. Lead and cadmium were quantified by graphite-furnace atomic absorption spectrometry, while Fe, Zn, Cu, and Mn were measured by ICP-AES but are not HMI metals.

Reported LOD/LOQ values were 1.3/4.4 ug/kg for Pb and 0.11/0.37 ug/kg for Cd. Recovery was 99.1 +/- 0.8% for Pb and 98.1 +/- 0.9% for Cd.

Related evidence

• Coffee
• Coffee
• Lead
• Cadmium

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