Author: Dicky Chen, Antonio Da Roza

Originally: Professor Wong Tze Wai, Department of Community and Family Medicine, CUHK (published by Civic Exchange)

Date: 10/8/10

Originally: June 2008

This literature review was commissioned by the Civic Exchange. It is a review of papers on air pollution and health, published in both local and international journals on medicine and health, with an emphasis on all-Chinese studies.

Its findings were as follows:

Outdoor Air Pollution and Respiratory Diseases & Symptoms Significant associations were found between dust storms and several respiratory symptoms (eg. coughing, sputum, shortness of breath, running nose, sneezing) as well as outpatient visits, in parents. Significant associations between PM10 and cough, as well as outpatient visits, in schoolchildren were also found.

There was a positive association between dust storms and PM10, but not CO or NO2.

100% of SO2 exposed residents in one study had mild to severe respiratory signs and symptoms, predominantly: chest tightness, cough, throat irritation, tears, and running nose. Children and the elderly were most affected. During the SO2 pollution episode, there was a 50% increase in clinic attendance for upper respiratory infections.

There was a higher mean score of cardiovascular symptoms among children living in a polluted district as compared with those living in a less polluted district.

Respiratory illnesses (phlegm, cough, phlegm without cold, cough without cold, bronchitis, and asthma) are affected mainly by PM10, then by NOx and SO2.

There were positive but statistically insignificant associations between air pollutants (PM2.5, SO2, NOx) and asthma.

There were, however, significant and positive associations between PM2.5, SO2, NOx and the prevalence of cough with cold, phlegm with cold, bronchitis and hospital admissions for respiratory disease.

There are significant positive associations between cough and outdoor air pollutants, passive smoking, coal burning, home heating in winter and cooking fumes. There is also a significant association between phlegm and outdoor air pollutants, passive smoking, home heating in winter and cooking fumes. Similarly, there was a significant association between bronchitis and outdoor air pollutants, coal burning, home heating in winter and cooking fumes, as well as significant positive associations between hospital admissions for wheezing, respiratory diseases, outdoor air and cooking fumes.

Higher prevalence rates of respiratory symptoms were found in moderately and high pollution districts in China, as compared to low pollution districts. Prevalence rates were higher in preschoolers than in schoolchildren.

Significantly higher prevalence rates of respiratory symptoms (cough without cold, phlegm with cold, doctor diagnosed asthma, doctor diagnosed bronchitis, current asthma and current bronchitis) were found in children, mothers and fathers living in polluted districts as compared with low pollution districts.

There was also a higher prevalence of rates of eye and respiratory illnesses (trachoma, conjunctivitis, nasal swelling, chronic rhinitis, tonsillitis and pharyngitis) in children living in polluted districts.

Among those aged 50 and above, there were significantly higher mortality rates in polluted districts.

Positive and significant associations between air pollutants and most respiratory symptoms (except asthma) were found in children and adults living in high pollution districts.

Positive and significant associations were found between quarterly mean SO2 concentrations and the percentage of bronchopneumonia cases among pediatric patients in hospital.

Parents’ history of respiratory illnesses proved to be significant risk factors for children’s respiratory signs and symptoms.

Air pollution was also found to be related to immune function.

Outdoor Air Pollution and Asthma PM10 was found to have the strongest adverse effect on asthmatic lung function. However, frequency of asthma and severity score was not significantly associated with air pollution.

The prevalence of asthma was higher in city dwellers and factory workers in China than in subjects from rural areas.

Children, especially those aged 3 and below, had a higher prevalence of asthma than adults.

More asthma attacks were found to have occurred in winter and spring.

Indoor air pollution was not significantly associated with asthma.

Outdoor Air Pollution and Chronic Obstructive Pulmonary Disease (COPD) A significant association has been found between COPD and outdoor air pollution, duration of firewood use, smoking, cooking and family history.

Higher blood pressure was found in all subjects (except boys aged 13-15) in polluted district as compared with a less polluted district. The urban group also had a higher lung cancer mortality rate than the reference group. Significantly lower lung function was found in the high pollution district, as compared with moderate and low pollution districts.

Growth rate of lung function was found to be significantly higher in the reference district than in the polluted district, for both genders. There was, however, no difference in the growth height and increase in body weight in the two districts.

The proportion of those with abnormal lung function was significantly higher in industrial, business, and high traffic districts than in clean districts. There was also a significantly higher rate of absence from school among the industrial, business and high traffic districts, as compared with clean districts.

Combustion of liquid petroleum gas, especially natural gas, may reduce lung function in children.

SO2 and NOx had no significant interactions with asthma; NO2 had significant interaction with bronchitis.

Outdoor Air Pollution and Mortality There is a positive and significant association between SO2 and non-accident mortality, and mortalities from COPD and CVD. There is a negative association between cancer mortality and SO2, but a positive and significant association between SO2 and total mortality and also respiratory disease mortality. There was also a positive but insignificant association between SO2 and mortalities from cerebrovascular disease and cancer. A significant association between SO2 and all cause mortality was also found.

There is a significant association between NOx and lung cancer mortality.

There are also positive associations between PM10 and lung cancer mortality.

Outdoor Air Pollution and ER / Hospital Admissions & Outpatient Department Visits There were significant associations between SO2 and daily outpatient department visits. There were also positive associations between air pollutant concentrations and ER and outpatient department admissions in respect of visits for pneumonia, colds and bronchitis.

A significant association was found between PM10 and daily outpatient visits for respiratory disease. There were significantly higher hospital admissions for respiratory diseases, COPD, and tumors in a high pollution district than in medium and low pollution districts.

Outdoor Air Pollution and Lung Cancer It was found that there was a significant association between lung cancer and SO2, but there was an insignificant association between annual lung cancer incidence and the mean annual concentrations of SO2 and NOx. There is a positive and significant association between lung cancer and PM10.

Air Pollution and Health Outcomes There are significant associations between hospital admissions (for all respiratory diseases, cardiovascular diseases, COPD, heart failure) and NO2, SO2, O3, and PM10.

There is a significant association between asthma, pneumonia, influenza and NO2, O3, and PM10. The prevalence of respiratory symptoms was higher in Kwai Tsing District than in South District, but not significantly so. There was also a higher prevalence of bronchial hyperreactivity in children from Kwai Tsing District.

For year-round admissions, the relationship with O3 was significant for all circulatory and heart failure admissions. SO2, NO2, and O3 had stronger effects on COPD admissions during the cold season (December to March) than during the warm season.


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