INTRODUCTION
We have recently described that chromium is a common contact allergen identified by patch tests in African countries.1 The minimal eliciting threshold concentration for hexavalent chromium (Cr(VI)) that results in 10% of patients having a positive patch test is 1 mg/kg (1 ppm).2 Cement is an important source of chromium exposure.3, 4 Since 2005, cement may not be used in countries of the European Union (EU) if the concentration of Cr(VI) is >2 mg/kg, which has significantly reduced the prevalence of allergic contact dermatitis (ACD) caused by cement in EU.3, 4 To determine whether Cr(VI) in cement could be a contributing cause to the high prevalence of ACD to chromium in African countries, we have performed an analysis of total chromium (Cr) and Cr(VI) in eight random samples of cement purchased in three African countries.

METHODS
Cement samples were randomly selected based on their availability in do-it-yourself markets in Tanzania, Ghana and South Africa. The chemical analysis of the cement samples was performed by ALS Denmark, Humlebæk. The total amount of Cr was measured by the standard DS 259:2003 (https://webshop.ds.dk/standard/52829/ds-259-2003) and DS/EN 16170:2016 (https://webshop.ds.dk/standard/M300697/ds-en-16170-2016). The amount of Cr(VI) was measured by the standard DS/EN 15002:2015 (https://webshop.ds.dk/standard/M279556/ds-en-15002-2015), DS/EN ISO 15192:2021 (https://webshop.ds.dk/standard/M336548/ds-en-iso-15192-2021) and DS/EN ISO 17294-2:2016 (https://webshop.ds.dk/standard/M287184/ds-en-iso-17294-2-2016).

RESULTS
Compared to a recently published analysis of 45 samples of cement from EU and non-EU countries,4 the total amount of Cr in the samples from the three African countries was relatively low (Table 1). However, the content of Cr(VI) was alarmingly high. In six out of the eight samples, the Cr(VI) content was ≥16 mg/kg, that is, more than eightfold higher than the maximal allowed concentration in the EU.

TABLE 1. Cement samples by country of origin with total and hexavalent chromium (Cr(VI)) content.a
Country/sample Total chromium (mg/kg) Cr(VI) (mg/kg)
Tanzania 1 28 16
Tanzania 2 31 16
Tanzania 3 26 4.6
South Africa 1 40 <0.2
Ghana 1 41 20
Ghana 2 46 21
Ghana 3 37 18
Ghana 4 60 23
EU countriesb 2.5–161.1 <0.1–10
Non-EU countriesb 6.1–595.2 <0.1–79
a Cr(VI) content in cement must not exceed 2 mg/kg in EU countries.
b Values from the study by Lejding et al.4
DISCUSSION
Historically, cement has been the most common and important cause of chromium allergy.3 Since regulations dictating that cement must not contain more than 2 mg/kg (2 ppm) Cr(VI) came into force in EU, ACD caused by cement has markedly been reduced in the EU countries.3, 4 The high frequencies of positive reactions to potassium dichromate in patch test studies from African countries suggest that exposure to chromium is high in these countries.1 Studies from Ethiopia, including occupational exposure, found that up to 67% of construction workers suffer from chromium allergy, supporting that cement could be a key source of exposure to chromium.1, 5 Our results support that a targeted effort in reducing the concentration of Cr(VI) in cement, for example, by adding ferrous sulfate,6 coupled with measures to prevent direct skin contact with cement could considerably reduce chromium allergy in at least two of the three African countries included in this study.