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Dalla Monografia della IARC, volume n.93-6, la fonte più importante per la ricerca del cancro,  si parla del carbon black e su uno studio su topi cita il Printex 90 diverse volte nel volume 93-6.

La cosa che mi ha stupito sono le caratteristiche descritte  del Printex 90, non tanto per le dimensioni di 14 nanometri, ma a me sembra, come vedo scritto, che contenga il  dei noti e potenti IPA cancerogeni (vedere lo scritto in  grassetto).

Un vecchio studio degli anni 80 confermava la presenza di questi IPA nei toner e la volontà di isolare ed eliminare queste impurità tossiche (Vedi studio riportato sotto).

E’ da capire se queste percentuali di IPA riportati nel Printex 90, siano un potenziale rischio per la salute, dato che molti patent di toner anche abbastanza recenti, come carbon black usano il Printex 90.

 

Dalla Monografia IARC 93-6:

Groups of 80 female Crl: NMRI BR mice, seven weeks of age, were exposed to highpurity furnace carbon black (Printex 90; primary particle size, 14 nm; specific surface area, 227±18.8 m2/g; MMAD of particles in the exposure chambers, 0.64 μm). The extractable organic mass of the carbon black was 0.04%; the content of benzo[a]pyrene was 0.6 pg/mg and that of 1-nitropyrene was <0.5 ng/mg particle mass.

The animals were exposed in whole-body exposure chambers for 18 hours per day on 5 days per week to 7.4 mg/m3 carbon black for 4 months followed by 12.2 mg/m3 for 9.5 months.

After exposure, the mice were kept in clean air for further 9.5 months.

A control group was exposed to clean air throughout the study. Histopathology was performed on the nasal and paranasal cavities, larynx, trachea and lung. After 11 months and up to 17 months, body weights were significantly lower (5–7%) in the carbon black-exposed mice compared with controls.

During the last months, no difference in body weight was observed between the groups. After 13.5 months, mortality was 20% in the carbon black-exposed mice and 10% in controls; 50% mortality was reached after 19 months in the carbon black-exposed group and after 20 months in the control group. In exposed mice, the lung particle burden was 0.8, 2.3 and 7.4 mg carbon black per lung after 3, 6 and 12 months, respectively; at 12 months, this corresponded to a lung particle burden of 37 mg/g cleanair

control lung (wet weight of control lung, 0.2 g). Tumours were only observed in the lung, but no statistical difference was observed between experimental and control animals; 11.3% (9/80) of carbon black-exposed mice had adenomas and 10% (8/80) had adenocarcinomas compared with 25% (20/80) and 15.4% (12/80) of controls, respectively (Heinrich et al., 1995).

 

Studio segnalante la riduzione del nitropirene nel carbon black del toner:

Nitropyrenes: isolation, identificaton, and reduction of mutagenic impurities in carbon black and toners.

Rosenkranz HS, McCoy EC, Sanders DR, Butler M, Kiriazides DK, Mermelstein R.

Abstract. Extracts of selected xerographic toners and copies were found to be mutagenic in the Salmonella assay. The activity was independent of the xerographic hardware and process and was traced to nitropyrenes present as impurities in the carbon black, the toner colorant. Manufacturing process changes resulted in a substantial reduction of the nitropyrene content of the carbon black and thus in the mutagenicity of the corresponding toners. Nitropyrenes are potent frameshift mutagens, and possible mechanisms for their biological action are discussed.