Risk assessment of drinking water from vending machines in the central area and support of establishment of the quality standard

Abstract

       The drinking water from vending machines greatly increased in the urban community, in particular, in 2011 Bangkok had more than 20,000 machines. During 2008-2012, data of many agencies showed that the quality of drinking water from vending machines failed to meet the standard based on the regulation of drinking water in sealed containers. As a result, consumers are vulnerable to hazards from the vended drinking water. In 2012, the Food and Drug Administration (FDA) intended to establish a certain quality standard of drinking water from vending machine. Consequently, a risk assessment of vended drinking water in five provinces in the central region of Thailand including Bangkok, Nonthaburi, Pathum Thani, Phra Nakorn Sri Ayutthaya and Saraburi was carried out during January to October 2012. The objectives were to obtain analytical data of vended water quality used for assessing the risk of foodborne illness and to support establishment of the national quality standard. Survey results of the water vending machines revealed that 76.9% of the machines were located in front of buildings and 69.3% were exposed to sunlight. Unhygienic surroundings of the water vending machines were found due to trash buckets / garbage and dirty water around the machine base at 10.9% and 9.3%, respectively. It was found that 60.0% of the vending machines were used not over than two years and only 3 (4.3%) from 69 legally enforced machines showed complete labelling conforming to the Commission on Labels No. 31 (B.E. 2553). Most water filtration systems inside the machines presenting 94.6% were reverse osmosis (RO) type. The analytical results showed that 121 (28.1%) of total 430 water samples from vending machines failed to meet the standard. For chemical results, 43 (10%) samples failed due to total hardness, pH and total solids presenting 6.5%, 3.5% and 1.6%, respectively. For microbiological data, 93 (21.6%) samples failed mainly due to Coliforms at 20.5% followed by E. coli at 3.7%. In addition, food poisoning bacteria were found in 8 (1.9%) samples and the heterotrophic plate count (HPC) greater than 1,000 CFU/ml was found at 71.8%. The Chi square test results showed that water vending machines upon sunlight exposure were not significantly related to the algae growth in dispensing chambers (P > 0.05, P = 0.4673), the analytical results of total hardness, total solids and microbiological data were not significantly related to working time of the water vending machines (P > 0.05, P = 0.6799, 0.5829 and 0.7753) whereas the poor quality microbiological results were significantly related to water vending machines with and without dispensing-chamber doors (P < 0.05, P = 0.0281). The risk of foodborne illness was calculated by the "Risk Ranger" program and the results indicated that the probability of illness per person per day among consumers in 5 provinces due to vended drinking water contaminated with S. aureus, C. perfringens and Salmonella spp. were 7.50 × 10^-9, 1.50 × 10^-8 and 7.50 × 10^-8, respectively. The expectation of illness incidents among 1,690,000 consumers in five provinces in the central area because of those three food poisoning bacteria were 14, 27 and 133 times per year with the risk ranking of S. aureus, C. perfringens and Salmonella spp. at 28, 29 and 39, respectively. The data and survey results were subsequently proposed to the FDA and in 2013, a notification of the Ministry of Public Health (No. 362) B.E. 2556 focusing on quality control of the drinking water from automatic machine was launched and was initially effective on 16 October, 2014.