3.3.4. Risk Level Determination

After defining the hazard and exposure bands, IN Nanotool allows the user to determine the risk level using a four-by-four matrix, as commonly used in other CB strategies [25]. This risk matrix is presented in Figure 11, and it is based on the matrix of the CB Nanotool 2.0.


**Figure 11.** IN Nanotool risk matrix. The darker the color the higher the risk level.

#### 3.3.5. Risk Control

The IN Nanotool aims not only to assess the risk of exposure to incidental metal nanomaterials, but also to help users to properly manage this risk by providing recommendations for risk control. These recommendations depend on the risk level and on the control measures already implemented. They aim to be an increment to the already existing measures. For each risk level, there is more than one recommendation. The user must analyze the options and select one (or more) that is not yet implemented and that can ideally have an impact on the higher scored factors. A new risk assessment may be performed after the implementation of the recommended controls, to validate the risk level decrease. However, when selecting the control, the user can take advantage of the tool to assess the impact of that measure in the risk level, helping to choose the more effective control measure. Table 9 shows the list of recommended additional control measures based on risk level.

#### *3.4. IN Nanotool—Case Study Application*

To experiment and verify the potential of IN Nanotool concept, this tool was applied to the SLM printer case study. The inputs had in consideration the MSDS and the technical sheet of the powder, the Portuguese Standard NP 1796:2014 (regarding the lowest OEL) [26], SEM results presented in Section 3.1, printer manufacturer information and in situ observation and consultation of workers. Table 10 shows the results of the application of the IN Nanotool to this case study.


**Table 9.** Recommended additional control measures based on risk level.

**Table 10.** Results of the application of the IN Nanotool.



**Table 10.** *Cont.*

<sup>1</sup> Carc. 2, H351 according to the material safety data sheet. <sup>2</sup> Skin Sens. 1, H317 and Stop RE 1, H372 according to the material safety data sheet. <sup>3</sup> Considering the lowest OEL recommended in Portugal: Nickel inorganic compounds (Portuguese Institute of Quality, 2014).
