Abstract
Recently, Borm and Driscoll published a commentary discussing grouping of Poorly Soluble particles of Low Toxicity (PSLTs) and the use of rats as an animal model for human hazard assessment of PSLTs (Particle and Fibre Toxicology (2019) 16(1):11). The commentary was based on the scientific opinion of several international experts on these topics. The general conclusion from the authors was a cautious approach towards using chronic inhalation studies in rats for human hazard assessment of PSLTs. This was based on evidence of inhibition of particle clearance leading to overload in the rats after high dose exposure, and a suggested over reactivity of rat lung cancer responses compared to human risk.As a response to the commentary, we here discuss evidence from the scientific literature showing that a) diesel exhaust particles, carbon black nanoparticles and TiO2 nanoparticles have similar carcinogenic potential in rats, and induce lung cancer at air concentrations below the air concentrations that inhibit particle clearance in rats, and b) chronic inhalation studies of diesel exhaust particles are less sensitive than epidemiological studies, leading to higher risk estimates for lung cancer. Thus, evidence suggests that the chronic inhalation study in rats can be used for assessing lung cancer risk insoluble nanomaterials.
Highlights
The mere availability of epidemiological evidence implies that human populations have been exposed to hazardous substances at sufficiently high levels to induce statistically significantly increased disease occurrence above background levels of lung cancer incidence
Particle clearance rates in mice, hamsters and rats depend on the lung burden: lower clearance rates are observed with increasing lung burden, but the impaired clearance is only observed in rats [3]
Based on the unit risk calculated from this large chronic inhalation study inhalation study [5], 1.3 extra lung cancer cases are expected per 100,000 exposed persons at an exposure level of 1 μg/m3 diesel engine exhaust in air
Summary
Many workers are exposed to particles and dust in the working environment. The mere availability of epidemiological evidence implies that human populations have been exposed to hazardous substances at sufficiently high levels to induce statistically significantly increased disease occurrence above background levels of lung cancer incidence. Mice and hamsters do not develop exposure-related lung cancer following 2 years inhalation of nano-sized particles whereas rats do [5]. Chronic inhalation exposure to carbon black nanoparticles (Elftex-12, 37 nm diameter) induces lung cancer in female rats at 2.5 and 6.5 mg/m3 [6].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
