Infection Risk Assessment with Exposure to Pathogens in the Flood Water - The case of City of Manila, Philippines

Transcription

1 Infection Risk Assessment with Exposure to Pathogens in the Flood Water - The case of City of Manila, Philippines Tran Thi Viet Nga 1 and Kensuke Fukushi 2 1 Institute for Environmental Science and Engineering, National University of Civil Engineering, Vietnam 2 Integrated Research System for Sustainability Science (IR3S), the University of Tokyo, Japan Presented by Psyche Fontanos, IR3S, UT International Conference on Sustainability Science in Asia 2012 Bali, Indonesia, January 12, 2012

2 JICA-WB-ADB Joint Study Climate Change Impact and Adaptation in Asian Coastal Mega-Cities Overall Framework JICA ADB World Bank alliance (Manila) (HoChiMinh City) (Bangkok, Kolkata) Case study of Metro Manila Methodology JICA IR3S alliance City Case Studies E.g. JICA: Metro Manila Coastal Engineering & Storm surge: University of Ibaraki River hydro: CTI International Transport: ALMEC Urban poor: Ateneo de Manila University Firms: National Statistics Office Health: University of Tokyo Solutions to Operations - Urban planners, local governments - Concerted donor efforts (e.g. World Bank, ADB, bilateral donors) 2 2

3 Metro Manila (Metropolitan Manila; National Capital Region, NCR) political, economic, social, cultural, and educational center of the Philippines 1 municipality, 16 cities (regional center is City of Manila) 11.5 M population based on 2007 census (13% of national pop.) 3

4 Flood Prone Areas in Metro Manila KAMAN AVA Area Pasig-Marikina Basin West Mangahan Area 4

5 Inundation in Metro Manila Infection Pathogens Wastewater/ Septic wastes 6

6 Research Objective Quantify the human health risks associated with exposures to pathogens in flood water Study area: City of Manila (Pop. 1.6M as of 2000) 7

7 8 Exposure to pathogens. 8

8 Calculation of Risk POPULATION Distribution of Population (City of Manila, 2000) < 4 years-old 5-14 years-old years-old > 60 years-old years-old 5-14 years-old years-old Outdoor time Contact time with flood water* >60 years-old Intake rate Ingestion volume* Dose *Daily activities and behaviors of each age groups were based on literature. **Ingestion volumes were derived from US-EPA Risk Assessment Guidance Infection risk TOTAL RISK 9

9 Inundation scenarios Level Inundation depth Description I 0-50 cm Most houses will stay dry and it is still possible to walk through the water II cm There will be at least 50cm of water on the ground floor III cm The ground floor of the houses will be flooded IV >200 cm Both the first floor and often also the roof will be covered by water *Classification was based on the Flood Fighting Act, Japan,

10 Assumptions Parameter Symbol Unit Notes Concentration of E. coli C E MPN/100ml A mean value of 30,000 MPN/100mL (18, ) was taken for E.Coli concentration in flood water (Nga, Master thesis, 1999) Water Ingestion Rate (indirect transfer during walking) Age <4 Age 5-14 Age Age >60 Water Ingestion Rate during swimming Age 5-14 Age Time spent outdoor Age <4 Age 5-14 Age Age >60 Fraction of outdoor time spent in water Dose-response model (Hass equation) N 50 α ml/hour ml/hour 50 ml/h 10 ml/h 10 ml/h 10 ml/h 100 ml/h 50 ml/h T hours/day Assumed 2 hours Assumed 4 hours Assumed 4 hours Assumed 1 hour F % Assumed, varies according to inundation levels (50-100%) 8.6x10^

11 Pathogen s dose-response model Beta Poisson model for E. coli(haas et al., 1999) For single infection risk: P( d) d α 1/ α N 50 where d = dose α = slope parameter = (derived) N50 = medium infectious dose = (derived) For annual infection risk: P 1 1 P( d) annual n where n = number of exposure times per year 12

12 Single risk and annual risk associated with pathogen exposure during flooding period Age Group Risk Inundation depth (cm) < > years-old 5-14 years-old yearsold >60 years-old Total Daily risk Total risk Daily risk Total risk Daily risk Total risk Daily risk Total risk Daily risk Total risk

13 Generation of Maps ArcGIS 9.2 by the US Environment Research Institute (US ESRI) Using the following data provided by the Metropolitan Manila Development Authority (MMDA) to create maps of population density, inundation and risk assessments. barangay boundaries of Metro Manila as of 2000 with the barangays in Manila City grouped together by District; statistics of population based on the census conducted by the National Statistics Office in 2000; and the GRID data of inundation scenarios Map of infected infectious people people Map of daily risk risk Inundation map Map of population density 14

14 Map of Population Density District 1 District 6 District 12 District 14 15

15 Inundation map 16

16 Map of Daily Risk and Infected People 17

17 Map of Daily Risk and Infected People, MM 18

18 Summary Contact with flood water poses significant human health risks for residents in the floodprone region like Manila, and particularly for poor children and youth. The risk of contracting gastrointestinal illness due to E. coli from accidental ingestion of flood water in Manila over the course of a year varies according to inundation levels and age. To verify the results, evidence of group behavior during floods, inundation water quality and natural, social and economic data pertaining to the study area need to be collected. This study hoped to make a contribution to the quantification of climate change-related risks, and to simulate further discussion and reflection on methodologies for undertaking quantitative assessments. Quantifying such risks can assist in future health planning (i.e., allocating clinic and health centers to more vulnerable areas) and community-based natural disaster risk management (i.e., prioritizing areas to respond to during a disaster, locating where to intensify flood awareness programs, etc) 19

19 References Donovan E., Unice K., Robert J.D., Harris M., and Finley B. Risk of Gastrointestinal Disease Associates with Exposure to Pathogens in the Water of the Lower Passaic River. Applied and Environmental Microbiology, Feb. 2008, p Dufour A.P, Evans O., Behymer T. D., and Cantu R. Water ingestion during swimming activities in a pool: a pilot study. J. Water Health 4: Charles N. Haas, Joan B. Rose, Charles P. Gerba. Quantitative microbiological risk assessment. John Wiley and Sons, NY, 1999 JICA, Metro Manila Flood Control Project Nga T.T.V. Master thesis. Asian Institute of Technology, US-EPA. Risk Assessment guidance for Superfund. Vol.1. Human health evaluation manual (Part A). EPA/540/1-89/002. US-EPA, Washington DC. Zoleta-Nantes, D Differential Impacts of Flood Hazards among the Street children, the Urban Poor and Residents of Wealthy Neighborhood in Metro Manila, Philippines. Journal of Mitigation and Adaptation Strategies for Global Change. 7(3): The Netherlands: Kluwer Publishing. 20

20 Thank you for your attention! Terima kasih!