PUB - Publikationen an der Universität Bielefeld

Background and Aim In the past three decades, China experienced a rapid economic growth and the Chinese urban population has increased threefold mainly caused by rural-to-urban migration. The rapid urban growth changes the cities’ living conditions with different effects on human health, which is particularly pronounced in China’s megacities. About 190 million migrant workers make up a large proportion of the urban population in China. They show health-related characteristics that differ from the situation of the urban residents. Among other things, migrant workers are under a higher risk for infectious diseases such as HIV and their mobility may foster the spread of infections between urban and rural areas. The rapid urbanization also causes substantial urban environmental problems. China belongs to the countries with the highest levels of particulate matter (PM) air pollution that is considered to be the most serious air pollutant in Chinese cities. The aim of this work was to obtain a comprehensive insight into the major urban health challenges in Chinese megacities. This research focused on two key urban health dimensions related to changing physical and social urban environments, (i) the urban PM air pollution and (ii) the rural-to-urban migration. Methods Firstly, a burden of disease assessment for the megacity of Hong Kong (HK) was conducted to describe the mortality-related burden of disease patterns of the Chinese urban population. Data were obtained from the HK statistical yearbook 2010 and from the HK Census and Statistics Department. The "Standard Expected Years of Life Lost" (SEYLL) measure was used to quantify the disease burden in HK by cause of death, sex and age for 2010. Secondly, two systematic literature reviews were conducted. In the first review, meta-analyses were carried out (i) to determine the HIV prevalence among migrants in China at different migration stages and (ii) to compare the risk of HIV infection among different migration stage subgroups and compared to the general Chinese population. The second review was done to collect PM data from the megacities in the Pearl River Delta (PRD). Additionally, mortality data from municipal sources were collected. The data were used (i) to describe the PM pollution in the megacities in PRD, (ii) to compare these results with the existing air quality standards and (iii) to estimate the potential health benefits of PM reduction in terms of preventable PM-associated premature deaths per year (health impact assessment). Thirdly, complementing the review on urban PM air pollution, own personal and ambient stationary PM2.5 air pollution measurements were conducted. For this purpose, in November and December 2011, 24-h personal and ambient PM2.5 data were simultaneously collected in most of the 12 districts of Guangzhou (GZ) (i) to ascertain the level of personal/ambient PM2.5 in GZ on a small spatial and temporal scale, (ii) to determine to what extent individuals, on average, were exposed to PM2.5 over 24h periods, and (iii) to study the relationship between the ambient and personal PM2.5. Results In HK, 524,706.5 life years due to premature death were lost. The following SEYLL-distribution was observed: 78.8% non-communicable conditions, 12.7% communicable conditions, 8.5% injuries. This distribution corresponds to disease patterns of high-income countries worldwide representing a late stage of the epidemiologic transition. A closer look showed that certain communicable conditions, such as tuberculosis play a larger role in HK than in many other high-income regions. Further results indicated high values of PM air pollution in the studied cities that exceeded internationally recognized air quality standards. Particularly in GZ, the PM air pollution was high. The relationship between ambient and personal measurements differed strongly between the districts. Three districts showed moderate to high correlations between ambient and personal PM2.5 pollution over time. However, the overall correlation (all district values pooled) between personal and ambient PM2.5 air pollution over time was high (Spearman’s Rho = 0.7; p = 0.01). According to the health impact assessment, PM air pollution is responsible for a large share of the burden of disease related to non-communicable diseases with thousands of premature deaths in HK and GZ. The review on the role of migration for the spread of HIV in China showed that the HIV prevalence among Chinese migrants ranged from 0-2.59% in the single review studies. The meta-analyses showed that the subgroup of migrants, who were recruited in urban areas after migration for the single studies, had the highest HIV prevalence (0.38%) as compared to the other subgroups and to the general Chinese population. Conclusions The results of this research highlight the increasing relevance of non-communicable diseases in urban China and indicate that this is related to both life style changes and environmental burdens like PM air pollution. Nonetheless, the findings suggest that communicable diseases are still of high public health relevance and that they are partly related to rural-to-urban migration. Consequent implementation of environmental protection laws and compliance with air quality standards are needed to promote a healthy urban environment. Living and working conditions of migrant workers should be improved and educational measures should be taken to decrease migrants’ risk for infectious diseases. Importantly, these conclusions must not lead to further stigmatization and discrimination of migrants within the urban societies. Reduced risk of infection among migrant workers and a better societal inclusion in the urban areas including better access to health care services would, in the long run, reduce the disease burden among migrants and additionally prevent epidemiological bridging from this group to the general Chinese population.