*2.3. Health Risk Assessment*

The health exposure assessment related to the inhalation of BTEXS compounds (excluding styrene) among the firefighters and office workers at a fire station in Poland was developed based on the methodology developed by the United State Environmental Protection Agency (US EPA) [24]. This assessment of the health exposure includes an assessment of the occupational carcinogenic risk (CR) associated with benzene inhalation, which was calculated according to Equations (1) and (2) [25], and an assessment of the occupational non-carcinogenic risk in terms of the threshold mechanisms of the toxic effects produced by compounds from the BTEXS group (expressed as hazard quotients, HQ), which were calculated according to Equations (1) and (3) [17].

$$\text{EC} = (\text{CA} \times \text{ET} \times \text{EF} \times \text{ED}) / \text{AT} \tag{1}$$

$$\text{CR} = \text{IUR} \times \text{EC} \tag{2}$$

$$\text{HQ} = \text{EC/(RfC} \times 1000 \text{ }\mu\text{g/mg)} \tag{3}$$

where CA is the chemical concentration (μg/m3). The other variables used in Equations (1)–(3) are explained in Table 1.

In the calculations, we assumed that inhalation constitutes 50% of all intake [26]. The risk assessment was carried out for the period of professional activity of the two groups of firefighters: (1) active (i.e., those involved in firefighting) and (2) office workers. Exposure duration (ED) and exposure frequency (EF) were assessed on the basis of interviews and observations. It was assumed that firefighters participating in rescue and firefighting operations perform 24-h shifts three times a week, while office workers work eight hours a day, five days a week. In 2018, firefighters from the analyzed unit responded to 643 fires (33 times in November 2018) [27]. Moreover, we assumed that both firefighters and office employees spend 50% of the work shift in conditions such as in the garage, while the remaining 50% of time is spent in conditions such as in the changing room. During the day, firefighters use, among others, the workshop and gym, which are located next to the changing room and garage. Office rooms and a dispatch room are also located next to or directly above these rooms. Therefore, we have adopted a simplification that in these rooms, BTEXS concentrations are comparable to those in the changing room and garage. The values of the individual parameters used to calculate the carcinogenic and non-carcinogenic risks are presented in Table 1.



\* The U.S. EPA provides two values of Inhalation Unit Cancer Risk (IURs) for benzene: 2.2 × <sup>10</sup>−<sup>6</sup> to 7.8 × <sup>10</sup>−<sup>6</sup> per 1 μg/m3. The higher IUR was used to obtain the maximum estimate of cancer risk from benzene exposure.
