A performance evalution of commercial steam sterilizers for medical wastes in Taiwan

• Main Authors: Hou-Wu Liu, 劉厚吾
• Other Authors: Chow-Feng Chiang
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/13341660210572464036

碩士 === 中國醫藥大學 === 環境醫學研究所碩士班 === 97 === The US Clean Air Act prohibits incineration of regulated medical wastes in general incinerators due to the high chlorine content (2.7%) of the wastes and the unstable operation conditions of the general incinerators. Under general conditions, the emission factor of dioxin can be as high as 3,000 μg I-TEQ/ton of medical wastes, i.e. 40 times of that from general refuse incineration. In Taiwan most medical wastes are being incinerated, resulting in very low material recovery. The Taiwan Environment Protection Administration has set a goal of recovery to be 45% for all types of municipal wastes by the year 2020. At present, only 2.5% of medical wastes are treated by sterilization and are recovered. The purpose of this study was to propose the use of a rapid readout method as an indicator of sterilization performance to sterilization of medical wastes and hence increase the recovery rate of medical waste materials. This study tested the effectiveness of a sterilization indicator under field conditions in sterilization facilities throughout Taiwan. In each facility, the effectiveness of a chemical indicator (CI) and a biological indicators (BI) were compared at 4 sampling sites: 1) challenge pack at the cold spot (CPC), 2) challenge pack at the middle chamber (CPM), 3) inside the bag (IB), and 4) inside the syringe in bag (IBS). The BI was monitored as a rapid readout (1~3 hr) and as a color change (24 hr). The effectiveness of BI was also tested by heterogeneous plate counts (HPC) using a pour plate technique. The CI was scored by degrees of color changes. The test results indicated that, among 10 sets of autoclaves being tested, 7 sets met the national microbial reduction standard (log kill ≧ 5), and three sets did not. Using CPC as the reference site, in 8 autoclaves evaluated, there was no significant difference (p > 0.05) in log kill between CPC and the other three sampling sites. Since CPC site gave a lower log kill, it was considered a relatively conservative reference site. In comparison with HPC, the sensitivity was 97.8% for the BI rapid readout, 90.7% for the BI color change, and 95.6% for the CI readout. In consideration of waste recycling, we also evaluated the sterilization efficiency for 3 types of plastic medical wastes (soft bag, soft tubing, and syringe) at two operating conditions: 121 oC/60 min by gravity displacement (121G) and 135 oC/45 min by vacuum displacement (135V). The results based on the two indication methods indicated that all the 121G tests failed to meet the national standard, whereas all the 135G tests complied with the standard. In addition, the sterilization efficiency of CPC was equivalent to those tested inside the three types of plastic wastes. This study concluded that 1) the current practice of medical waste sterilization in Taiwan needs improvement, 2) standard operation and auditing procedure need to be established, 3) the use of challenge pack with CI and BI appeared to be a reliable and convenient method, and 4) sterilization at 135 oC by vacuum displacement for 45 minutes is a viable pretreatment method for medical waste recycling.