| With the development of society and economy, continuous improvement of life, work environment and working conditions of the people has become true, many public places are installed the fully closed central air conditioning equipment. Since the SARS outbreak in2003, there are increasingly vocal about desire to public environmental including live, office, business and entertainment and air hygienic quality, we have had further understanding and attention on public health security. A lot of studies have reported that many central fan air conditioning systems of public places have serious pollution, which has potential hazard to human health. Therefore, the problems of indoor health safety of central fan air conditioning systems of public places have drawn great attention from the public. The hypothesis of central fan air conditioning systems may be a transmission route of infectious disease also has drawn great attention from departments of public health under local people’s governments at or above the county level and the public. Therefore, the Ministry of Health has enacted a series of regulations and standards, with the aims to strengthen public health management on central air conditioning ventilation system and ensure the public health safety and people’s health.1ObjectiveTo understand the current status of Legionella-contamination to centralized air conditioning system of public places and its seroprevalence among related populations in Shaoxing, and to provide decision-making basis for comprehensive management to prevent and control outbreak of infectious disease of the respiratory system, so as to promote the health safety of concentrated air conditioning in the public place and keep people healthy.2Methods2.1The source of the cooling water samples and testing itemsIn2009summer and winter, central air-conditioning system cooling tower water was randomly selected from public place including hotel, market, supermarket, hospital, securities companies, and office buildings in Shaoxing city. Testing items contain Legionella pneumophila.At the same time, we randomly checked the dust in blast pipe of centralized air conditioning system, and the testing items include dust quantity, total number of bacteria in dust, and fungus.2.2Assignment and selection of subjects Non exposed groupDuring2009to2010,500health workers were selected from the work place that the Legionella pneumophila was not detected from cooling water, and these workers have continually worked in the place for at least5years. Exposed groupDuring2009to2010,500health workers were selected from the work place that the Legionella pneumophila was detected from cooling water, and these workers have continually worked in the place for at least5years.2.3Analysis methodsAll data was analyzed using the statistical package for the social sciences (SPSS for Windows, version10.0; SPSS Inc., Chicago, IL, USA) software. A two-tailed P value<0.05was used to denote statistical significance.3Results3.1Testing result of cooling waterA total of42public places including including hotel, markets, supermarket, hospital, securities companies, and office buildings were selected as study filed, where440cooling water samples were collected and tested. The result of testing showed that Legionella pneumophila detection rate of cooling water was67.3%(74/110). The detection rate of cooling water selected from supermarkets, hospitals, securities companies, hotels, markets, office buildings were82.4%(14/17),78.6%(11/14),71.4%(5/7),66.0%(33/50),62.5%(10/16) and16.7%(1/6) respectively.From August to September, we detected59cooling tower water samples of central air-conditioning system from42public places, the detection rate was72.9%(43/59) The detection rate of cooling water selected from supermarkets, hospitals, securities companies, hotels, markets, office buildings were88.9%(8/9),77.8%(7/9),66.7%(2/3),70.4%(19/27),75.0%(6/8) and33.3%(1/3) respectively.From February to March, we detected51cooling tower water samples of central air-conditioning system from42public places, the detection rate was60.8%(31/51) The detection rate of cooling water selected from supermarkets, hospitals, securities companies, hotels, markets, office buildings were75.0%(6/8),50.0%(4/8),60.9%(14/23),80.0%(4/5),75.0%(3/4) and0%respectively.3.2Dust quantity of blast pipe and its testing results3.2.1Dust quantity of blast pipe and its testing results in2009In August2009, we detected blast pipe of centralized air conditioning system of4hotels,4supermarkets and2markets. Of the10public places,7were moderately polluted,3were severe polluted (Table3-7). The detect results showed that:(1) The maximum, minimum and mean of dust quantity of blast pipe was41.27g/m,0.21g/m2and19.03g/m2. The mean value of hotels, supermarkets, markets was23.64g/m2,17.91g/m2and7.50g/m2respectively.(2) The maximum, minimum and mean of total number of bacteria in dust was54000cfu/g,260cfu/g and7900cfu/g. The mean value of hotels, supermarkets, markets was5400cfu/g,12500cfu/g and5500cm/respectively.(3) The maximum, minimum and mean of total number of fungus amount was870000cfu/g,300cfu/g and83000cfu/g. The mean value of hotels, supermarkets, markets was110000cfu/g,67000cfu/g and59000cfu/g respectively.(4) Moderately polluted places account for70%and severe polluted places account for only30%, which indicated that blast pipe of centralized air conditioning system is generally present3.2.2Dust quantity of blast pipe and its testing results in2010In August2010, we detected blast pipe of centralized air conditioning system of9grand hotels,4hotels,4hospitals,1supermarket and1market. Of the19public places,14were moderately polluted,3were severe polluted (Table3-8). The detect results showed that:(1) The maximum, minimum and mean of dust quantity of blast pipe was56.04g/m2,0.34g/m2and10.62g/m2. The mean value of grand hotels, markets, supermarkets, hotels and hospitals was6.08g/m2,12.83g/m2,26.83g/m2,14.27/m2and12.58/m2respectively.(2) The maximum, minimum and mean of total number of bacteria in dust was68000cfu/g,410cfu/g and13000cfu/g. The mean value of grand hotels, markets, supermarkets, hotels and hospitals was7200cfu/g,16000cfu/g,32000cfu/g,17000cfu/g and15000cfu/g respectively.(3) Slight polluted places account for10.52%, moderately polluted places account for73.68%and severe polluted places account for15.79%.3.3Results of serum Legionella antibody3.3.1Results of serum Legionella antibody among health population Among520health peoples,25positive Legionella antibodies were detected and positive rate was4.81%.10positive samples were selected from students and the positive rate was3.92%.15positive samples were selected from minding workers and the positive rate was5.66%.3.3.2Results of serum Legionella antibody among exposed groupAmong520exposed peoples,76positive Legionella antibodies were detected and positive rate was14.87%.36positive samples were selected from supermarket workers and the positive rate was18.95%.14positive samples were selected from market workers and the positive rate was14.89%.35positive samples were selected from securities companies staffs and the positive was14.29%.21positive samples were selected from hotel staffs and the positive rate was10.94%.4ConclusionCentralized air conditioning system in public places has been severe polluted by Legionella and blast pipe was subject to dust quantity and microbial contamination in Shaoxing city. It is necessary to strengthen monitoring and control of Legionella in centralized air conditioning system in public place including hotels, supermarkets and hospitals. Therefore, we may provide decision-making basis for comprehensive management and reliable foundation that can promote sanitation standard of central heating ventilation and air conditioning systems in public places to national standard, which can prevent and control spread of microbial contamination and ensure hygiene quality of aid in public place and ensure the safety and security of people. |
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