Study of Concentrations of Pm2.5 in the Air at Selected Sites in Nairobi and Their Relationship to Respiratory Diseases Reported in Local Hospitals

Abstract

Fine particulate matter (PM2.5) refers to dust or aerosols (droplets floating in the air) with a diameter of at most two and a half microns and once inhaled by a person, settle in the lungs, specifically the alveoli. Many empirical studies have shown an association amongst PM and the occurrence of respiratory illnesses among all age categories of humans. This research examined association amongst concentrations of PM2.5 in the air and reported incidence of respiratory ailments at selected sites within Nairobi County in the period January 2017 - December 2020. Data on reported incidences of respiratory diseases (pneumonia, upper respiratory tract infections) were obtained from Mutuini, Mbagathi and Mama Lucy hospitals between January 2017 to December 2020 and used for the study while three hourly data on PM2.5 concentrations in the air from August 2019 to January 2020 were obtained from six air sampling points located in Embakasi, Kawangware, Kibra, Baba Dogo, Dandora, and Langata using an E sampler. Correlation, regression and exploratory analysis conducted on the data established that the PM2.5 concentrations were, several times in the 24 - Hour period, higher than WHO recommended limits by as much as 4.7 times in some sampling sites but generally lower than NEMA ambient air quality guidelines during most of the time in the 24 - Hour period. The highest concentration levels of PM2.5 were observed at the times of peak vehicular traffic (that occurs between 4pm and 8pm) in the Nairobi area and therefore it is highly likely that vehicular traffic significantly contributed to fine PM pollution in Nairobi. Hospital data showed that children under five years of age constituted at least 52.8% of all the patients that visited the three hospitals and were diagnosed with respiratory related illnesses. Additionally, there was a positive relationship amongst PM2.5 concentrations in Kibra and reported incidents of respiratory illnesses in Mutuini, Langata and Mbagathi Hospitals. There is however a negative correlation between PM2.5 concentration in Kawangware and reported cases of respiratory illnesses in Mama Lucy Hospital. Based on the findings, vehicular traffic significantly contributes to PM2.5 pollution in Nairobi. There is need for implementation of existing regulations to reduce PM2.5 pollution as well as introduction of policies to control and reduce vehicular emission which are significantly responsible for increased PM2.5 concentration during the day. Additionally, there is need for government intervention in installation of air pollution measurement sensors aimed at acquiring long term data to trigger further research in this field.