Hong Kong ( CNN ) -- Several Chinese cities have shown improvements with air quality information -- a politically-sensitive issue in China -- but improvements are still needed , according to a Beijing-based non-profit environmental group . The report by the Institute of Public and Environmental Affairs assessed air quality monitoring in 113 cities across China . The cities with the most transparency in air quality data included Guangzhou , Shenzhen and Beijing , with the most improved cities being Guangzhou , Nanjing and Nanning . Compared with the organization 's last report based on 2010 data , Chinese cities have made significant progress , said Ma Jun , the founding director of the Institute of Public and Environmental Affairs . `` Some Chinese cities have moved forward , '' he said . `` Among all 113 cities , there is still a large number of them which are not making proper disclosure . '' In January , Beijing started releasing information about air pollutants in finer detail by looking at the presence of smaller pollutants , PM2.5 , which are particulate matter smaller than 2.5 micrometers . The previous standard was PM10 . Smaller particles are believed to pose major health risks including risks of premature death , heart and lung diseases , according to the U.S. Environmental Protection Agency . Analysts blame the thick haze that regularly shrouds the country 's cities on rapid urbanization and industrialization . Beijing , for instance , burned some 27 million tons of coal in 2010 , according to state-run media . Despite efforts to limit the number cars with an auto-plate lottery , it 's estimated that Beijing now has over 5 million cars , up from about 3.5 million in 2008 . Pollution is more acute because of the sheer size of the city 's population ( 17 million ) and the rapid speed of its economic growth , experts say . Some cities need time to get new air quality monitoring machines and to train new staff to operate them , Ma said . The worst level of disclosure of city air quality data was in western China , he added . Western China is less industrialized than its eastern counterpart . But economic differences may not fully explain why some cities lag in releasing air quality data . `` We do notice that there are some other cities which are highly polluted , for example steel cities in the Shandong province . Their pollution level is very high , but they are not making much disclosure , '' he said . Chinese authorities have been accused of not properly assessing the extent of the problem , prompting U.S. diplomatic missions across China to provide air pollution information to the American community so that `` it can use to make better daily decisions regarding the safety of outdoor activities , '' according to U.S. Officials in June . The U.S. readings are widely viewed as a reliable alternative to the official index maintained by China 's Environmental Protection Bureau . Derived from a monitoring station in each of the embassy grounds , they typically paint a starker portrait of air quality than official reports , often falling within `` unhealthy '' bands , as defined by a rating system developed by the U.S. Environmental Protection Agency . But this independent monitoring has provoked an angry response in China . In June , a senior Chinese official demanded that foreign embassies stop issuing air pollution readings saying that embassies lacked legal authority to monitor the environment . Beijing has now added 35 new monitoring locations and ranks as the top city in monitoring for smaller pollutants , according to the Institute of Public and Environmental Affairs ' report . By August 2012 , over 55 cities and 192 places published PM 2.5 data , the report added . `` There have been progress significantly in a very short period of time -- thanks to the push made by extensive public participation , '' Ma said . Despite some progress , other Chinese cities have lagged behind . Twenty-nine cities , including Chongqing â€ ” China 's biggest metropolis -- Hohhot , Zhengzhou , Shenyang , Jinan , Hefei , Changsha and Urumqi , did not publish any information . Cities with highest air quality information transparency . 1 . Guangzhou . 2 . Shenzhen . 3 . Dongguan . 4 . Zhongshan . 5 . Beijing . Cities with lowest air quality information transparency . 1 . Jingchang . 2 . Qujing . 3 . Rizhao . 4 . Jining . 5 . Weifang .
Environmental nonprofit conducted air quality monitoring in 29 Chinese cities . Report by environmental nonprofit examined openness of Chinese air quality data . But 29 Chinese cities publish no data about air quality .