Black toner

Status:

completed 03/2002

Aims:

The potential health hazards arising from the use of laser printers owing to harmful toner constituents were reported frequently in the course of 2001. These reports gave rise to uncertainty among the public. The objective of the project was to establish the emissions of toner substances (respirable and inhalable dust fractions), aromatic hydrocarbons and ozone actually arising during printing from standard laser printers. The metal content of the toners was also to be analysed. The results were to permit conclusions concerning the potential health hazards presented by the use of black & white laser printers, and to promote corresponding technical improvements by the manufacturers where applicable.

Activities/Methods:

The following parameters were recorded for a total of eight laser printers from leading manufacturers: release of inhalable and respirable dust, release of aromatic hydrocarbons, release of ozone, toxicologically relevant effects in the luminescent bacteria test, and the content of various metals in the toner samples. The studies into the emission behaviour were performed in continual operation in a closed test chamber (volume approx. 9 m³) under conditions similar to those employed in Project 7005, "Health hazard assessment of colour toner dust".

Results:

The results concern toner dust, ozone formation, and total volatile organic compounds (TVOC). During the printing process, the black & white laser printers studied did not release toner dust in quantities exceeding the detection limits of the measurement methods employed. The detection limits are 0.6 mg/m³ (GSP 10) and 0.16 mg/m³ (VC 25 G). Nickel and cobalt were not detected in any of the four toner samples studied in quantities above the detection limits of the method employed. The detection limits concerned were 0.010% by mass for nickel and 0.020% by mass for cobalt for the three toners containing iron, and 0.002% by mass for nickel and cobalt for the iron-free toner. Tin, which may also be contained in toners in the form of organic tin compounds, was likewise not detected above the detection limits. The detection limits for tin were 0.040% by mass for the three toners containing iron, and 0.020% by mass for the iron-free toner. Should these metals be absorbed through the respiratory system, the detection limits stated above for dust release (0.16 mg/m³) yield maximum possible concentrations of 0.000016 mg/m³ for nickel, 0.000032 mg/m³ for cobalt and 0.000048 mg/m³ for tin for the toners studied. Ozone formation by laser printers has ceased to be a problem. Many products already employ technology which is completely ozone-free. Of the products studied, only one was found to release ozone, in a concentration of 18 ppb. This value is substantially below the applicable atmospheric limit value and other assessment levels for exposure of eight hours' duration. Total volatile organic compounds (TVOCs) are emitted by all laser printers in varying quantities. The quantities emitted by all products studied, however, comprised only a fraction of the applicable atmospheric limit values over eight hours' exposure. The quantities of benzene emitted by the laser printers are of the same magnitude as the background benzene levels in the environment. As it is not possible to specify a threshold value for the carcinogenic action of benzene, the manufacturers are nevertheless urged to develop product technology further with the objective of eliminating benzene emissions as far as possible. Two of the eight studied laser printers demonstrate that this goal is attainable.

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