23. Cremations and other chromium-containing combustion materials

In 2019, owing to legal restrictions, the German Environment Agency (UBA) investigated 25 model ashes from cremations of empty coffins in five cremation furnaces. All contained Cr(VI). In extraction with 0.01 M CaCl₂, ash/solution 1:50, an average of 17 % of total chromium went into solution; the dissolved chromium was present entirely as Cr(VI). The report describes process-related chromium inputs and soil/groundwater risks. Calcium is present mainly as calcium phosphate; total calcium is not proof of free CaO. [44]

Exhaust gas emissions, residual ash and the subsequent release from an urn are separate exposure or environmental pathways. An emission factor does not describe an ash concentration; an eluate test does not describe exposure via breathing air. The technical context is nevertheless the same reason for investigation: the chromium source, reactive basic components, the temperature-time profile and the atmosphere of the process must be recorded together. Which specific chromate phase is formed is clarified by suitable speciation and phase analysis.

The Porto reference 10216/21130 belongs to Ferreira, Almeida and Pinto (1999): Influence of temperature and holding time on hexavalent chromium formation during leather combustion. Leather scraps were investigated. According to the publisher's abstract, Cr(VI) was below 5 mg/kg before combustion; relevant quantities dependent on temperature and holding time were formed in the ashes. The source supplements the thermal Cr(III)/Cr(VI) conversion in chromium-containing combustion material. The abstract was evaluated; the study does not concern human cremations. [45]