Roof-Collected Rainwater Consumption and Health

Transcription

1 Roof-Collected Rainwater Consumption and Health Stan Abbott and Brian Caughley Roof Water Harvesting Centre Massey University Wellignton New Zealand

2 Risk Assessment of Roof Water Tanks Risk Assessment Risk Analysis Risk Acceptability? Risk Identification Risk Estimation Consequence Analysis Risk Communication Public vs Expert Perceptions of Risk Understanding Science of RWH Burden of Proof Costs vs Benefits of RWH Adapted from Rowe (2007) Risk Management

3 What is a Public Health Risk? Hazard: Micro-organism or chemical that may cause sickness if it contaminates the water Event: Incident or situation that may introduce a hazard into the water Likelihood: What are the chances of it happening? Consequence: If it did happen how bad would it be?

4 Hazards Associated with Roof Water Harvesting Injury (e.g. From ladder falls - gutter cleaning) Drowning or near-drowning Asphyxiation Poisoning Infection

5 Asphyxiation Drowning or Near Drowning

6

7

8

9 E.coli and Enterococci per gram faeces (Geldreich 1976; Jones & White 1984) Animal E.coli Enterococci Common sea gull 52,600,000 90,000 Starling 10,000 11,800,000 Sparrow 25,000 1,000,000 Pigeon 10,000 11,500,000 Blackbird 9,000 11,250,000 Robin 25,000 11,700,000 Duck 33,000,000 54,000,000 Chicken 52,600,000 90,000 Rat 180,000 78,900,000 Mouse 330,000 7,700,000 Cat 7,900,000 27,000,00 Man 13,000,000 3,000,000 Cow 230,000 1,300,000 Sheep 16,000,000 38,000,000

10 Adapted from Heyworth (2004)

11 Adapted from Heyworth (2004)

12

13

14 Survey of Private Roof Water Dwellings in NZ (DEFICIENCIES) (Abbott, Caughley & Douwes 2007) Deficiencies included: * Lack of maintenance * Inadequate disinfection or no treatment * Poorly designed delivery systems and storage tanks

15

16

17

18

19

20

21 560 Water Samples Total coliforms and E.coli (Colilert - IDEXX) 5 year Study of Private Dwellings (Stand Alone Roof Water Supplies)

22 Roof Water Quality of Private Dwellings in NZ (Abbott, Caughley & Douwes 2007) Range per 100ml (N = 560) (Total coliforms) (Escherichia coli) (32%) 202 (36%) (6%) 56 (10%) (9%) 72 (13%) (12%) 84 (15%) (11%) 90 (16%) > (30%) 56 (10%)

23 Faecal coliform Surveys of Private Roof-Collected Rainwater Supplies Year Location Number (N) Failed (%) Range (CFU/100ml) 1983 Micronesia Thailand Hawaii USA North Island (NZ) > Rural Australia Australian Farms Rural Auckland Wairarapa Farms > /06 New Zealand >2420

24 HOW MANY REPORTED DISEASE OUTBREAKS LINKED TO ROOF-COLLECTED RAINWATER?

25 Categorizing Levels of Evidence of Disease Microbiology/water quality: A = Pathogen identified in patient is also found in water. B = Water quality failure and/or water treatment problem of relevance but outbreak pathogen not detected in water. (Tillet et al 1998) PLUS Epidemiology: C = Evidence from an analytical (case-control or cohort) study demonstrates association between water and illness. D = Descriptive epidemiology suggests that the outbreak is water related and excludes other obvious alternative explanations. Strongly associated - if (A+C) or (A+D) or (B+C) Probably associated - if (B+D) or C only or A only Possibly associated - if B only or D only.

26 DISEASE OUTBREAKS LINKED TO ROOF-COLLECTED RAINWATER cases Salmonellosis (DT160) - Auckland cases Salmonellosis - Queensland cases Salmonellosis - Auckland cases Salmonellosis - Trinidad cases Campylobacteriosis Queensland cases Legionnaires disease Carribean cases - Torres Strait Islands Dengue Fever ( ) Giardiasis & Cryptosporidiosis Melbourne

27 DISEASE OUTBREAKS LINKED TO ROOF-COLLECTED RAINWATER cases Legionnaires disease Auckland cases Salmonellosis (DT9) - Melbourne cases Norovirus Turoa Ski Field NZ

28

29

30 Sewage system failure? Human access to the roof catchment area?

31

32

33 Water sources used for making snow

34 Few reported outbreaks may be due to: Under- reporting - few individuals involved (???) Transient populations dispersal of cases Sporadic illness Mild illness then less likely to seek medical attention Possible immunity in some individuals Asymptomatic infection Kiwi joker syndrome

35 Waiheke Island New Zealand 4,550 Dwellings 6,000 Tanks 7,500 8,000 Population 25,000 30,000 Summer Population Are AGI Disease Rates Up??

36 Roof Water Compliance (MOH 2009/2010) Type All roof water- only supplies Compliant 6.5% 6.4% Non-compliant 37.5% 61.0% Not monitored 56.0% 32.6% School roof water supplies Compliant 8.9% 9.5% Non-compliant 41.5% 45.8% Not monitored 49.6% 44.7% Are AGI Disease Rates Up?? Why the high non-compliance??

37 Reasons for Non-compliance Inadequate sampling Non-recognised laboratory analysis E.coli transgressions Inadequate corrective action following transgression

38

39 ROOF WATER CONSUMPTION EPIDEMIOLOGICAL STUDIES Case-control study New Zealand Campylobacteriosis (Eberhart-Phillips et al 1997) Prevalence study South Australia (Heyworth 2006) Case-control study New Zealand Giardiasis (Hoque et al 2003) Case-control study Tasmania Salmonellosis (Ashbolt & Kirk 2006) Double-blinded randomised control (Rodrigo et al 2010)

40 Waterborne Disease Surveillance Underestimate the rate of disease Only capture case-patients in contact with a healthcare system Not all persons infected by enteric pathogens develop gastrointestinal symptoms Less than a third of persons with an GID seek medical care Stool samples for laboratory diagnosis are only obtained in a minority of cases (Wheeler et al 1999; Hunter et al 2003; Roy et al 2006 )

41 Epidemic versus Endemic/Sporadic Disease Frost et. al (2003) Craun et. al (2004)

42 Reporting Pyramid for AGI in NZ 2006 Lake, Adlam, Perera, 2007 (ESR / NZFSA AGI Study) 1 Notified 3.5 Positive Tests 17.5 Specimens Submitted 19 Faecal Specimens Requested 48 Visits a GP 219 Community Cases

43 Bacterial Indicators and Diarrhoeal Disease Incidence of diarrhoea in young children related to water quality (>1000 E.coli /100ml) But little difference in illness rates in children using either good quality water (<1 E.coli /100ml) or moderately contaminated (2-100 E.coli /100ml) (Moe et al 1991)

44 Outbreaks of Disease Associated with PWS (Said et al 2003; Jones et al 2005) England & Wales PWS serve 0.5% (300,000 people) % of Drinking Water Outbreaks 25 Outbreaks cases 5190 people at risk (52% Campylobacter implicated) Canada PWS serve 13.0% (4,000,000 people) 20% of Drinking Water Outbreaks 45% (Additional) Rural/Remote

45 Contributing Factors Implicated in PWS Outbreaks Temporary or transient populations (88%) Treatment (Lack or Failure) (80%) Presence of animals (52%) Heavy rains (preceding outbreak) (24%)

46

47 Campylobacter Notifications June 2005 (843 Cases) (EpiSurv - Monthly Surveillance Data) Of the 85 cases (10%) for whom information was available: 53 (62.4%) consumed food from a food premise 31 (32.6%) reported contact with farm animals 12 (14.1%) reported contact with other symptomatic people How many of the 90% of unknowns consumed untreated (roof?) water?

48