## 3 Results  
### Toxicological Evaluation  
Table 2 shows the toxicological parameters, health-based guidance values and air quality standards for the protection of human health established by the different national and international organizations, found by our literature search. The toxicological parameters included the Lowest Observed Adverse Effect Level (LOAEL) and the No Observed Adverse Effect Level (NOAEL) from experimental studies for both short and prolonged exposure to outdoor ozone, established by Health Canada [3]. A LOAEL of 120 ppb for short exposure to ozone (up to 4 h) (Table 2) was obtained from studies in humans, showing lung function decrements and increased breathing frequency [7; 8; 9; 10] after controlled exposure to ozone. For longer exposure (from 4 to 8 h), [PERSON] [17; 18] investigated the effects of 6.6 h exposure in healthy adults while doing intermittent exercise; one of these studies [17] considered different exposure levels (40, 80 and 120 ppb) to establish the dose-response relationship. Since this study found no significant effects occurred at the lowest exposure level of 40 ppb, compared to subjects exposed to filtered air, this concentration was set as the NOAEL for prolonged exposure (Table 2). Significant effects were seen at 80 and 120 ppb, with greater decreases in pulmonary function and increases in respiratory symptoms at 120 than at 80 ppb. Therefore, the LOAEL was set at 80 ppb for this duration (Table 2). Health Canada also derived a Reference Concentration (RfC), which is a health-based guidance concentration below which there should be a negligible risk of adverse health effects after lifetime exposure. The RfC was estimated by dividing the experimentally derived NOAEL by the uncertainty factor of 10 for intra-species variability. This RfC should be used for a recommended Maximum Exposure Limit (MEL) for residential indoor environments (Table 2), taking account of the feasibility of achieving such a limit. An exposure limit based on the RfC of 4 ppb for prolonged ozone exposure, however, was considered not achievable in many homes, mainly because of the outdoor ozone concentrations [21]. Health Canada therefore established a MEL of 20 ppb for ozone, based on an average time of 8 h. Consequently, for our study we took 20 ppb as a safe ozone concentration that should not be exceeded in indoors for long exposure, considering the ozone released from the dryer during its normal operation, plus outdoor ozone concentration. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**S (mg/h)** & **P (Unitless)** & **V (m3)** & **K\({}_{\text{d}}\) (h\({}^{-1}\)) a** & \(\lambda\) (h\({}^{-1}\)) a & \(\text{C}_{\text{0}}\)(ug/m3) a \\ \hline
5 & 1 & 15 & 3.75 \(\pm\) 2.10 & 0.51 \(\pm\) 0.68 & 42.5 \(\pm\) 41.8 \\ \hline \hline \end{tabular}  
* values as mean \(\pm\) standard deviation. Legend: S = ozone source emissions; P = penetration of the building shell; V = room volume; K\({}_{\text{d}}\) = ozone decay rate (calculated from the t \(\frac{1}{2}\) of 16.01 min measured in our laboratory experiments); \(\lambda\) = air exchange; C\({}_{\text{0}}\) = mean annual ozone concentration using data from the Regional Protection Agency.  
\end{table} 
Table 1: Values assigned to each parameter of the mass-balance model. Air quality standards defined by the European Union (EU) [19] and World Health Organization (WHO) [20] refer to long and short exposure to outdoor ozone (Table 2), and come from an assessment of the effects of ozone exposure on life expectancy. The \"information threshold\" and the \"alert threshold\" indicate the outdoor ozone concentrations above which, after a short exposure of 1 h, there is a health risk in the most sensitive sub-population, such as people with asthma or cardiovascular diseases (\"information threshold\", 90 ppb), and the general population (\"alert threshold\", 120 ppb) [22].