## 1 Introduction
One of the less studied air pollutants, is carbon monoxide (CO), commonly known with the nickname of \"Silent Killer\". The association between CO and health is incontrovertible, the gas increasing the risk of acquiring both a respiratory or a circulatory type disease [45; 46; 47; 48]. Besides these primary pollutants, there is a secondary one much researched (mainly in the last years), the ozone (O\({}_{3}\)), that reveals a connection with the population's health, especially when related to respiratory diseases [49; 50; 51; 52; 53; 54; 55]. Table 1 shows a pertinent bibliography concerning air pollution and population health. This study focuses on PM\({}_{10}\), NO\({}_{2}\), NO, CO, and O\({}_{3}\). As previously demonstrated in many studies, these pollutants are closely associated with health impacts, so we followed the main findings and analyzed the air pollution relationship with all respiratory diseases and all circulatory diseases, then singled out all cardiac diseases--in specific ischemic heart disease, cerebrovascular disease, acute upper respiratory infections, and chronic lower respiratory diseases. That being said, we are not discussing whether the disease is caused by air pollution or is an _a priori_ condition, or if it is based on an acute or chronic episode; we are exploring the occurrence of an episode and its relationship with air pollutants. The health data refers to daily hospital emergency admissions (HA) in the SNS (Portuguese National Health Service). The data comprises 11 years, from 2005 to 2015, and concerns the Lisbon Metropolitan Area (LMA). \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & **ACD** & **CARD** & **HDD** & **CD** & **ARD** & **CKDD** & **AURI** \\ \hline CO & [PERSON] et al., 2013[56] & [PERSON] et al., 2017[57] & [PERSON] et al., 2019[58] & [PERSON] et al., 2018[66] & [PERSON] et al., 2019[48] & [PERSON] et al., 2014[62] & [PERSON] et al., 2019[64] \\  & [PERSON] et al., 2019[64] & [PERSON] et al., 2020[59] & [PERSON] et al., 2020[79] & [PERSON] et al., 2020[60] & [PERSON] et al., 2020[61] & [PERSON] et al., 2020[63] & [PERSON] et al., 2019[64] \\ NO & - & [PERSON] et al., 2013[66] & [PERSON] et al., 2019[64] & [PERSON] et al., 2019[64] & - & - & - \\  & [PERSON] et al., 2020[65] & [PERSON] et al., 2020[67], & [PERSON] et al., 2020[76] & [PERSON] et al., 2011[72] & [PERSON] et al., 2016[74] ; [PERSON] et al., 2016[75] ; [PERSON] et al., 1997[7] ; [PERSON] et al., 2013[66] & [PERSON] et al., 2020[99] & [PERSON] et al., 2020[71] & [PERSON] et al., 2014[72] & [PERSON] et al., 1991[71] & [PERSON] et al., 2020[75] ; [PERSON] et al., 2020[75] \\ O\({}_{3}\) & [PERSON] et al., 2021[53] & [PERSON] et al., 2007[66] & [PERSON] et al., 2019[58] & [PERSON] et al., 2020[56] & [PERSON] et al., 2020[56] & [PERSON] et al., & [PERSON] et al., 2020[75] \\  & [PERSON] et al., 2024[79] & [PERSON] et al., 2017[55] & [PERSON] et al., 2013[62] & [PERSON] et al., 2020[54] & [PERSON] et al., 2019[49] & 2020[56] & [PERSON] et al., 2016[64] \\ PM\({}_{20}\) & [PERSON] et al., 2014[21] & [PERSON] et al., 2015[96] & [PERSON] et al., 2017[96] & [PERSON] et al., 2020[72] & [PERSON] et al., 2020[75] & [PERSON] et al., 2019[95] & [PERSON] et al., 2018[96] \\  & [PERSON] et al., 2016[88] & [PERSON] et al., 2019[51] & [PERSON] et al., 2019[91]: & [PERSON] et al., 2017[90] & [PERSON] et al., 1992[94] & [PERSON] et al., 2020[79] & 2020[97] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Studies that analyze the relationship between air pollutants and diseases. All circulatory diseases (ACD), cardiac diseases (CARD), ischemic heart disease (HID), cerebrovascular diseases (ARD), chronic lower respiratory diseases (CLRD), and acute upper respiratory infections (AURI).