The Rises of Coronavirus Disease (COVID-19) death rate in Japan with high PM2.5


 Currently vulnerable age groups in most countries are affected by the respiratory -coronavirus disease 2019 (COVID-19). Long-term-exposure to high levels of PM2.5 (particulate matter with aerodynamic diameter ≤ 2.5μm) is also associated positively with repository deaths. The aim of this study is to find if high PM2.5 levels affect COVID-19 caused deaths in Japan. COVID-19 caused death and tested positive cases in all prefectures during the study period from Feb. 18 up to Apr. 16, 2020 are analyzed. PM2.5 caused deaths from 2010 to 2017 are calculated based on PM2.5-relative risk (RR) of 1.04 (95% CI: 1.01 – 1.08) from the World Health Organization-Air Quality Guidelines (WHO–AQG). The findings of this study show that old people who are living in prefectures with high levels of PM2.5 are the most vulnerable to COVID-19. The estimated death cases from 2010 to 2017 are about 115,532 (95% CI: 28,883 - 231,064) cases. Thus; policy decision makers could consider PM2.5 data to support their efforts not only to minimize the spread of COVID-19, but also to improve air quality.


Introduction
A recent study from Wuhan, China, by Zhou F., et al., (2020) has shown an association between adverse health effects among elders and COVID-19. Another recent study from United State by Wu X., and Nethery R., (2020) has examined the association between long-term exposure to air pollution and COVID-19 deaths, they found a strong association between elevated PM 2.5 and increased COVID-19 death rates. In Japan, the information issued by the Ministry of Health, Labor and Welfare (MoHLW) show that, up to April 16, 2020, there are 4,168 tested positive and 81 death cases caused by COVID-19 (Ogiwara K, 2020). Long-term-exposure to high levels of PM 2.5 (particulate matter with aerodynamic diameter ≤ 2.5μm) is also associated positively with repository deaths (Pope III et al., 2002;Pope III and Dockery, 2006;Lippmann, 2009;Jerrett et al., 2009). Additionally, in Japan there are many published studies listed in Nawahda (2012 and2014) about the effects of PM 2.5 on human health. Thus; the information about the distribution of PM 2.5 levels and COVID-19 deaths and tested positive cases, from Feb. 18 up to Apr. 16 th , 2020, in all prefectures in Japan are analyzed. The deaths due to long-term exposure to PM 2.5 are calculated from 2010 to 2017 based on the relative risk (RR) of 1.04 (95% CI: 1.01 -1.08).
This RR value is associated with 10 μgm −3 change in PM 2.5 mean annual concentration (Pope III et al., 2002).
The findings of this study show that old people who are living in prefectures with high levels of PM 2.5 are the most vulnerable to COVID-19. Thus; this study provides a better understand of possible association between air quality management and COVID-19 and the corresponding policies to minimizing the adverse effects on human health.

Coronavirus COVID-19 Japan Cases
MoLHW provides the following information related to COVID-19 cases in Japan; tested positive, with symptoms, discharged, PCR tested, serious, deaths, and by ages for all prefectures in Japan. Fig. 3., shows the number of reported death cases up to April 16 th , 2020, most of the cases belong to +60-year age group.

Effect of long-term eexposure to PM 2.5
The annual deaths caused by long-term exposure to high levels of PM 2.5 are calculated as follows, where x is the prefecture index, t is the year of simulation, pop is the exposed population, i is the index of age group, △PM 2.5 is the change in the annual mean levels, M b is the annual mean baseline death rate, and β PM2.5 equals 0.004 (Nawahda, 2014). An increase of 10 μgm -3 annual mean of PM 2.5 caused a 4% (95% CI: 1.01-1.08) increase in death rate for the age group of +30-year (Pope III et al., 2002).
The Population of all 47 prefectures in Japan in 2015 is collected from the database of the Official Statistics of Japan (e-stat, 2015). The population is divided into four age groups, 0-14; 15-64; 65-74; and +75. The corresponding percentage of each age group is as follows, 13.76%; 66.08%; 11.05%; and 9.11%, respectively. The corresponding baseline mortality (per one thousand) of each group is as follows, 0.3; 2.25; 14.28; and 59.01, respectively (Nawahda, 2014). The first two age groups are ignored due to the limitation of Eq.
(1) that is valid for +30-year age groups.

Results And Discussion
The calculated annual deaths in all prefectures in Japan from 2010 to 2017 caused by exposure to PM 2.5 > 10 μgm -3 for the +65-year age groups are listed in Table 1. The calculated death cases due to exposure to PM 2.5 >10 μgm -3 during the study period from 2010 to 2017 are shown in Fig. 4. The death cases among the +75-year age group are around 3.4 times as much as the third age group. Better air quality of the year 2017 compared to 2010 could save the lives of around 13,600 inhabitants. Figure 5, shows that that old people who are living in prefectures with high PM 2.5 levels are the most vulnerable to COVID-19.
The calculated death cases due to exposure to PM 2.5 in all prefectures in Japan are estimations based on RR value of 1.04. These estimations are conservative; if a higher value of RR is considered, e.g. 1.08 (Jerrett et al., 2009) for PM 2.5 levels > 10 ugm-3, the estimated deaths will increase accordingly. In 2009 Japan Ministry of Environment (MoE) adopted the following air quality standards of PM 2.5 ; 15 μgm -3 /35μgm -3 (mean annual standard / 24 hours standard). These standards are similar to the U.S.EPA PM 2.5 -guidelines (USEPA, 2010) but different from the World Health Organization-Air quality Guidelines (WHO-AQG), which are; 10 μgm -3 /20 μgm -3 (WHO, 2005). According to Figures 2 and 6 the mean annual standard is met almost in all prefectures in Japan. This indicates a yearly improving air quality. However; during the study period the 24 hours standard is exceeded mainly in the southern prefectures in Japan. This could be due to the yellow dust storms.
There is uncertainty in the method of estimating the effects of long-term exposure to high levels of PM 2.5 as discussed in (Nawahda, 2014). This uncertainty is mainly caused by using a non-Asian CR function and population data (e.g. counts, percentage of each age group, and the corresponding baseline mortality) of the 8year study period.

Conclusion
The aim of this study is to find if PM 2.5 affects COVID-19 caused deaths in Japan. data to support their efforts in minimizing the spread of COVID-19.

Declarations
The author of "The Rises of Coronavirus Disease (COVID-19) death rate in Japan with high PM2.5" declares no competing interests.  Distribution of COVID-19 related tested positive and death cases up to April 16th, 2020, Japan.

Figure 4
Distributed death cases for the age groups +65 years in Japan from 2010 to 2017.

Figure 5
Distribution of deaths and reported tested positive COVID-19 cases (up to April 16, 2020) in Japan.