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. 2022 Apr:26:100396.
doi: 10.1016/j.impact.2022.100396. Epub 2022 Mar 17.

Towards health-based nano reference values (HNRVs) for occupational exposure: Recommendations from an expert panel

Maaike Visser  1 , Ilse Gosens  2 , Delphine Bard  3 , Pieter van Broekhuizen  4 , Gemma Janer  5 , Eileen Kuempel  6 , Michael Riediker  7 , Ulla Vogel  8 , Susan Dekkers  2
Affiliations

Towards health-based nano reference values (HNRVs) for occupational exposure: Recommendations from an expert panel

Maaike Visser et al. NanoImpact. 2022 Apr.

Abstract

Unique physicochemical characteristics of engineered nanomaterials (ENMs) suggest the need for nanomaterial-specific occupational exposure limits (OELs). Setting these limits remains a challenge. Therefore, the aim of this study was to set out a framework to evaluate the feasibility of deriving advisory health-based occupational limit values for groups of ENMs, based on scientific knowledge. We have used an expert panel approach to address three questions: 1) What ENM-categories should be distinguished to derive advisory health-based occupational limit values (or health-based Nano Reference Values, HNRVs) for groups of ENMs? 2) What evidence would be needed to define values for these categories? And 3) How much effort would it take to achieve this? The panel experts distinguished six possible categories of HNRVs: A) WHO-fiber-like high aspect ratio ENMs (HARNs), B) Non-WHO-fiber-like HARNs and other non-spheroidal ENMs, C) readily soluble spheroidal ENMs, D) biopersistent spheroidal ENMs with unknown toxicity, E) biopersistent spheroidal ENMs with substance-specific toxicity and F) biopersistent spheroidal ENMs with relatively low substance-specific toxicity. For category A, the WHO-fiber-like HARNs, agreement was reached on criteria defining this category and the approach of using health-based risk estimates for asbestos to derive the HNRV. For category B, a quite heterogeneous category, more toxicity data are needed to set an HNRV. For category C, readily soluble spheroidal ENMs, using the OEL of their molecular or ionic counterpart would be a good starting point. For the biopersistent ENMs with unknown toxicity, HNRVs cannot be applied as case-by-case testing is required. For the other biopersistent ENMs in category E and F, we make several recommendations that can facilitate the derivation of these HNRVs. The proposed categories and recommendations as outlined by this expert panel can serve as a reference point for derivation of HNRVs when health-based OELs for ENMs are not yet available.

Keywords: Engineered nanomaterials; Expert panel; Health based; Nano reference values; Occupational exposure limit.

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Figures

Fig. 1.
Fig. 1.
Uncertainty in the level of protection (left) and effort needed to decrease the uncertainty in the level of protection (right).
Fig. 2.
Fig. 2.
Schematic view of the different steps in the Expert Panel Approach used in this project. CP = Core Panel, RP = Review Panel.
Fig. 3.
Fig. 3.
Graphical representation of proposed HNRV categories, characteristics of the categories and recommendations and considerations on HNRV values described in this article. * For example, workplace exposure limits recommended by the U.S. NIOSH (NIOSH, 2013) or the Danish NFA (Poulsen et al., 2018).
See this image and copyright information in PMC

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