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Biosolids case study, Drexel December 2013

Biosolids case study, Drexel December 2013

Published in: Education, Health & Medicine

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  • Changed developing countries to india since our focus is india and perhaps difficult to extrapolate?
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  • Deleted “due to its occupational engagement in the developing nations”
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  • Not sure if there were any edits to map, but it was showing up corrupted in my version
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  • Transcript

    • 1. QMRA on Municipal Solid Waste Dumps in India Anne Thebo Bharathi Murali Parnab Das Peiying Hong 1
    • 2. Problem Statement & Motivation 2
    • 3. 3
    • 4. Problem Statement: To assess the risk due to the microorganisms that the rag pickers are exposed to. Motivation: To determine if it is possible to formally legalize the rag picking business without Legend: Dumping sites 1, 2, 3, 4 are near to the residential district Dumping sites 5, 6 and 7 are located further away Dumping site 8 is a control site (construction waste) Assume 1 million population in this city, with 1% of 4 population being rag pickers
    • 5. Goals of this QMRA • • • • What is the magnitude of health risks faced by rag pickers? Which pathogen(s) pose the greatest risks to rag pickers? How does risk vary across dumping sites? What interventions would be most appropriate for: 1. Mitigating health risks faced by rag pickers? 2. 5 Minimizing secondary transmission?
    • 6. Hazard Identification 6
    • 7. Hazard ID • Proteus sp. • Bacillus sp. • Klebsiella sp. • Salmonella sp. • Escherichia coli • Staphylococcus aureus • Pseudomonas aeruginosa 7
    • 8. Hazard ID • Proteus sp. • Bacillus sp. • Klebsiella sp. (Klebsiella pneumoniae) • Salmonella sp. (S. enterica serovar Typhi) • Escherichia coli (Enteroinvasive E. coli) • Staphylococcus aureus • Pseudomonas aeruginosa 8
    • 9. Exposure routes & assessment 9
    • 10. @Risk Populations 10
    • 11. Exposure Routes Klebsiella pneumoniae Salmonella Typhi Escherichia coli (EIEC) Staphylococcus aureus Candida albicans 11
    • 12. Data Provided • Dump Sites: – – Bacteria and fungi (CFU/g) – • Approximate location Probability of transmission to rag pickers Rag Pickers: – Microorganism observation frequency by site – Microorganism observation frequency by sample type (stool/urine/nasal swab/sputum) – Blood/Immune/Liver function 12
    • 13. Data  Exposure Bacteria & Fungi isolated from different dump sites and control sites, CFU/g 1 2 3 4 5 6 7 - 1.2 x 106 - 1.1 x 106 - - 0.1 1.2 x 106 1.2 x 106 1.4 x 106 1.1 x 106 1.4 x 106 1.2 x 106 1.1 x 106 - - - 1.1 x 106 - - 0.2 x 106 - - 1.9 x 106 1.3 x 106 1.1 x 106 1.2 x 106 - 1.4 x 106 1.1 x 106 1.2 x 106 1.2 x 106 - BACTERIA/FUNGI Candida sp. Escherichia coli Klebisiella sp. Salmonella sp. Staphylococcus aureus 2.1 x 106 1.4 x 106 1.4 x 106 1.2 x 106 8 Exposure factors from USEPA Activities (adult male, 21-31 yrs) Soil and dust ingestion Hand to eye-lip-nostril contact 50 15.7 Units mg/day times/h Dermal exposure - adherence of soil to face 0.024 mg/cm2/d Dermal exposure - adherence of soil to arms 0.0379 mg/cm2/d Dermal exposure - adherence of soil to hands 0.1595 mg/cm2/d Dermal exposure - adherence of soil to legs 0.0189 mg/cm2/d Dermal exposure - adherence of soil to feet Working week Working hours 0.1393 6 6 mg/cm2/d d/wk h/d BACTERIA /FUNGI Candida sp. Escherichia coli Klebsiella sp. Salmonella sp. P (transmission to rag picker from dump site) 0.002 0.004 0.002 0.001 Staphylococcus aureus 13 0.001
    • 14. Data  Exposure 1. Ingestion dosage Ingestion through mouth contact Klebsiella sp. conc in MSW Hands to mouth 1.1 x 106 15.7 P(transmission) K. pneumoniae Total per dose 0.002 0.1 4330.18 Accidental ingestion of soil CFU/g times/h Klebsiella sp. conc in MSW Soil and dust ingestion Fraction CFU P(transmission) K. pneumoniae Total per dose 1.1 x 106 50 CFU/g mg/day 0.002 0.1 11 Fraction CFU 2. Subcutaneous dosage Subcutaneous exposure Klebsiella sp. conc in MSW Exposure 1100 0.3796 P(transmission) K. pneumoniae 0.002 0.1 Subcutaneous dose CFU/mg mg/cm2 Fraction 0.83512 CFU/ cm2 14 Sum 4341.176 CFU/d
    • 15. Dose- response assessment (modeling methods) 15
    • 16. Analysis Steps 1. Evaluate data availability 2. Identify availability of dose response curves 3. Select “planned” model – Exponential or β-Poisson 4. Estimate dermal and ingestion exposure 5. Estimate k for Klebsiella sp. and Candida sp. 6. Model using “planned” model 7. 16 Evaluate modeling results/appropriateness
    • 17. Data Availability & Background Exposure Route Ingestion Ingestion Ingestion Ingestion Dermal Pathogen Escherichia coli Salmonella sp. Proteus sp. Bacillus sp. Staphylococcus aureus Klebsiella sp. Dermal/Ingestion (Klebsiella pneumoniae) Candida sp. Ingestion (Candida albicans) Pseudomonas Dermal aeruginosa Dermal Streptococcus sp. Airborne Aspergillus sp. Observed in study sites? Y Y Y Y Y Observed Have Dose in rag Response Have Best Fit pickers? Relationship? Model? Y Y Y Y Y Y N N/A N/A N N/A N/A Y Y Y Y Y Y N Y Y Y N N No Data Y Y Y N Y N N Y N N Frequency of microorganism occurrence: Dump Site: S. aureus = E. coli > Salmonella spp. Rag Pickers: S. aureus > E. coli > Salmonella spp. 17
    • 18. Modeling Approach Pathogen Status Escherichia coli enterotoxigenic enteroinvasive enteropathogenic Salmonella Typhi Staphylococcus aureus Klebsiella pneumoniae Candida albicans # of Available DR Models Modeled Modeled Modeled Modeled Modeled Modeled (w/derived DR) Modeled (w/derived DR) 14 7 4 3 3 1 N/A N/A Planned Model β-Poisson β-Poisson β-Poisson β-Poisson Exponential Developed Exponential Dose Response Developed Exponential Dose Response Final Model Reference Exponential Exponential Exponential Exponential Exponential QMRAwiki Haas et al. 1999 Du Pont et al. 1971 Powell 2000 Hornick 1970 Rose et al. 1999 Exponential See next slide Exponential See next slide • Evaluated available dose response models • Built Excel model – • 1000 iterations 18
    • 19. Approximation to exponential model 1. Gather LD50 available in published literature 2. Substitute known values to determine k LD50 Strain KP1-O Response k 7.20E+00 Death Ave Read off the LD50 dose, Proceed same way as before Stdev 9.63E-02 6.50E+00 values 1.07E-01 1.01E-01 0.007331 3. Use determined kDeath for Monte Carlo 19
    • 20. Risk characterization 20
    • 21. Risk Characterization: Risk across different sites S. Typhi C. albicans K. pneumoniae (ingestion) K. pneumoniae (subcutaneous) E. coli (EIEC) S. aureus • Population at risk 1.00E+04 8.00E+03 6.00E+03 • 4.00E+03 2.00E+03 0.00E+00 1 2 3 4 5 Dumping sites 6 7 8 • Sites 4 and 6 face risk from >2 pathogens (i.e., S. Typhi, E. coli, C. albicans & S. Typhi, E. coli, and K. pneumoniae) Sites 1, 2, 3, 5 and 7 face risk from 2 types of pathogen Site 8 (control site) has no known pathogenic 21
    • 22. Risk Characterization: Risk across different pathogens Dumping sites/ pathogens 1 E. coli (EIEC) 6.56E-03 S. Typhi 6.07E-01 S. aureus 1.36E-05 Risk per year (Maximum allowable risk = 10-4 or 1 in 10,000 population) 2 3 4 5 6 7 6.56E-03 8 7.63E-03 6.02E-03 7.63E-03 6.56E-03 6.02E-03 5.47E-01 4.23E-01 3.76E-01 4.15E-01 1.36E-05 1.16E-05 1.36E-05 1.07E-05 1.16E-05 1.16E-05 K. pneumoniae (ingestion) 6.37E-01 1.72E-01 K. pneumoniae (subcutaneous) 9.22E-01 3.88E-01 C. albicans • 1.00E+00 1.00E+00 6.95E-06 Authorities should be more concerned of the pathogens in descending priorities of: C. albicans = K. pneumoniae = S. typhi > E. coli (EIEC) > S. aureus 22
    • 23. Sensitivity Analysis • Sensitivity Analysis – 3 strains of pathogenic of E. coli – 3 different ratios of Pathogenic EC:EC – 3 different concentrations of E. coli in MSW 23
    • 24. Strains of Pathogenic E. coli and Model Type β-Poisson Exponential Strain Path EC:EC Dose N50 α Annual Risk K (estimated) Annual Risk Enteroinvasive (EIEC) 0.001 96.73 2.1*106 0.155 2.6*10-3 2.2*107 5.4*10-3 Enterotoxigenic (ETEC) 0.001 96.73 8.6*107 0.178 3.7*10-5 2.2*108 5.3*10-3 Enteropathogenic (EPEC) 0.001 96.73 6.9*107 0.221 1.0*10-5 2.2*108 5.3*10-3 EIEC – Exponential Model EIEC - β-Poisson Model f(x) = NaNx 15 R² = NaN Risk (P(I)/d) Risk (P(I)/d) 15 10 5 0 0 2 4 6 Dose(mg/d) 8 10 12 10 5 0 0 2 4 6 Dose(mg/d) 24 8 10 12
    • 25. Ratio of Pathogenic E. coli to E. coli Strain Path EC:EC Dose (CFU/d) K (estimated) Annual Risk enteroinvasive 0.001 96.73 2.2*107 5.4*10-3 enteroinvasive 0.01 967.26 2.2*108 6.5*10-2 enteroinvasive 0.1 9672.60 2.2*108 1.0 f(x) = NaNx R² = NaN 12 Risk (P(I)/d) 10 8 Linear () 6 4 Linear () 2 0 Linear () 1 10 Dose (mg/d) 25
    • 26. Study Limitations • Quality of input microorganism data questionable – • Detection methods – described methods not sufficient for listed microorganisms Dose response relationships – Some extrapolated from animal models – Dose-response models for three of the pathogens are not available in QMRA Wiki (Candida, Staphylococcus aureus, Klebsiella spp.) • – • Estimated from LD50 Switch from β-Poisson to exponential model Need to assume strains present (based on available dose-response curves) – – Salmonella spp. reported – • Indicator E. coli reported Most other MO reported as genus (generic) rather than specific species Precise dumping site locations unknown 26
    • 27. Risk management 27
    • 28. Intervention measures • Microbial risks: Sites 4 and 6 > Sites 1, 2, 3, 5 and 7 • Proximity to residential district Sites 1, 2, 3, 4 nearer than Sites 5, 6, 7 (human flux to residential district is impeded by the presence of a forest reserve) • Legend: Dumping sites 1, 2, 3, 4 are near to the residential district Dumping sites 5, 6 and 7 are located further away Dumping site 8 is a control site (construction waste) Approach 1: Encourage rag picking activities in Sites 5 28 and 7, with a localized
    • 29. Intervention measures • • C. albicans = K. pneumoniae = S. Typhi > E. coli (EIEC) > S. aureus Treatment removal efficiency of following should be achieved: K. pneumoniae S. Typhi C. albicans 1.30E+02 6.50E+04 2-log removal 4.60E-01 1.52E+05 5.70E-03 7.67E+04 6-log removal 7-log removal 0.00E+00 5.00E+04 1.00E+05 1.50E+05 2.00E+05 29
    • 30. Other Management Strategies Sites Strategies suggested 1 ● Usage of PPE (gloves, ● shoes, mask) Periodic immunization, ◊ medical screening Risk communication/ □ education at basic level Installation of a collection ᴥ center 2 3 4 ● ◊ ● ◊□ ● ◊ v v v 5 ● 6 ●□ᴥ 7 ● # 2, 3, and 4 has high annual risk due to Candida albicans and K. pneumoniae. Usage of PPE at all the sites would reduce the dermal exposure significantly Risk communication strategies could minimize secondary transmission across sub-populations 30
    • 31. Future Work • Conduct additional sampling – – • • Concentrations on rag pickers Proportion of pathogenic strains and identity Check modeling assumptions Better characterization of input variable uncertainty • More rigorous sensitivity analysis • Evaluate additional dose response models 31
    • 32. References • QMRA Wiki (CAMRA) • USEPA Handbook of Exposure • • Wachukwu C.K., Mbata C.A., Nyenke C.U. (2010) The Health Profile and Impact Assessment of Waste Scavengers (Rag Pickers) in Port Harcourt, Nigeria. Journal of Applied Sciences 10: 9168-1972. Chandramohan A., Ravichandran C. (2010) Solid waste, its health impairments32 role of and
    • 33. References • • • Wennerås C, Erling V (2004) Prevalence of enterotoxigenic Escherichia coli-associated diarrhoea and carrier state in the developing world. J Health Popul Nutr 22: 370-382 Wingard J.R., Dick J.D., Merz W.G., Sandford G.R., Saral R., Burns W.H. (1982) Differences in virulence of clinical isolates of Candida tropicalis and Candida albicans in mice. Infection and Immunity 37: 833-836. 33 Cryz Jr S.J., Furer F., Germanier R (1984)