Lead exposure in a municipal water system: City of Ottawa Case Study. ODWAC presentation. September 16 th, 2016

Transcription

1 September 16 th, 2016 Lead exposure in a municipal water system: City of Ottawa Case Study ODWAC presentation Ian Douglas, P.Eng. Penny Wilson Andy Campbell

2 Case study: Ottawa 1) typical lead profile at tap 2) household water use patterns 3) geographic distribution of pre-1955 homes 4) how many children are affected? ph corrosion control phosphate treatment no corrosion control 5) Relative lead contributions: air, food, dust, water 6) How effective is phosphate treatment 7) lead removal by in-home filters 8) how effective is tap flushing

3 ~15,000 15,000 Partial LSL Lead Copper Lead Lead

4 < > 20 Number of Results MOECC lead results histogram of winter vs. summer L1 & L2 samples from MOECC in-home lead testing (n=1500 homes) ppb Lead conc. (ppb)

5 Factors affecting tap water lead exposure? ph temperature length of service pipe diameter of pipe galvanic corrosion flowrate stagnation period tap flushing water chemistry corrosion control? household plumbing type of faucet (eg. brass) time of consumption household water use patterns amount consumed particulate vs. dissolved

6 How does lead concentration vary at the tap? Lead conc (ppb) Average lead concentrations at kitchen tap for house with Partial & (flowing & 30-min stagnation; summer; n=10 homes) Partial LSL Flowing 1st Litre 2nd Litre 3rd Litre 4th Litre 5th Litre 6th Litre 7th Litre 8th Litre

7 Water use patterns in a typical family home? 1-week flow surveillance at 2 homes with young families flowrate monitored every minute x 7 days average duration between water use events = 34 min for <4 minute water takings, average volume = 3.3 Litres average # of water taking events = 54 per day average duration of water use = 204 min/day

8 Water use patterns in a typical family home? dishwasher laundry?

9 Water use patterns in a typical family home? leaking toilet?

10 Theoretical Lead Solubility vs. ph X Ottawa

11 Treatment options pilot & full-scale trials 1. Current strategy (control) ph ppb 2. Elevated ph ph ppb 3. Phosphate ph mg/l as P 1 2 ppb Summer 2016 trial ph 9.4

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13 Distribution of pre-1960 homes (LSL) City of Ottawa

14 Potential lead exposure pattern in municipal water supply City of Ottawa (population 875,000; 10.8% <9 yrs old) Corrosion control with ph=9.2 (summer) 10% BAD 8.2 ppb % 90% 3.8 ppb 6,380 Older homes (Pb) [ ] normal 1.9 ppb 7,090 30% Post-war (Cu) [ ] 0.4 ppb 28,300 55% 0.4 ppb 52,000 New home (Cu) [ ] [Pb]tap # of children

15 Potential lead exposure pattern in municipal water supply City of Ottawa (population 875,000; 10.8% <9 yrs old) Corrosion control with ph=9.2 (summer) 50% 10% BAD 8.2 ppb % (Pb/Pb) 90% 3.8 ppb 6,380 Older homes (Pb) [ ] 50% normal 30% Post-war (Cu) [ ] Partial LSL (Pb/Cu) 1.9 ppb 0.4 ppb 7,090 28,300 55% 0.4 ppb 52,000 New home (Cu) [ ] [Pb]tap # of children

16 Potential lead exposure pattern in municipal water supply City of Ottawa (population 875,000; 10.8% <9 yrs old) Corrosion control with ph=9.2 (summer) 50% 10% BAD 8.2 ppb % (Pb/Pb) 90% 3.8 ppb 6,380 Older homes (Pb) [ ] 50% normal 30% Post-war (Cu) [ ] Partial LSL (Pb/Cu) 1.9 ppb 0.4 ppb 7,090 28,300 55% 0.4 ppb 52,000 New home (Cu) [ ] [Pb]tap # of children

17 Estimated tap water lead exposure for various house types (weighted mean [Pb] based on fraction consumed assume no in-home filter) Lead concentrations - estimated based on sampling (n=1100) & pilot plant testing I. ph corrosion control (ph=9.2) Old house full LSL Old house full LSL"BAD" Old house partial LSL New house (Cu) Water portion Lead conc. (µg/l) fraction consumed Lead conc. (µg/l) fraction consumed Lead conc. (µg/l) fraction consumed Lead conc. (µg/l) fully flushed (>2min) min stagnation in plumbing min stagnation in LSL (L3/L4) Pb conc: fraction consumed II. PO4 corrosion control (ph=7.5) Old house full LSL Old house full LSL"BAD" Old house partial LSL New house (Cu) Water portion Lead conc. (µg/l) fraction consumed Lead conc. (µg/l) fraction consumed Lead conc. (µg/l) fraction consumed Lead conc. (µg/l) fully flushed (>2min) min stagnation in plumbing min stagnation in LSL (L3/L4) Pb conc: fraction consumed III. no corrosion control (ph=7.5) Old house full LSL Old house full LSL"BAD" Old house partial LSL New house (Cu) Water portion Lead conc. (µg/l) fraction consumed Lead conc. (µg/l) fraction consumed Lead conc. (µg/l) fraction consumed Lead conc. (µg/l) fully flushed (>2min) min stagnation in plumbing min stagnation in LSL (L3/L4) Pb conc: fraction consumed

18 Potential lead exposure pattern in municipal water supply City of Ottawa (population 875,000; 10.8% <9 yrs old) Corrosion control with ph=9.2 (summer) 15% Older homes (Pb) [ ] 50% 50% (Pb/Pb) 90% 10% BAD normal (710) (6,380) [Pb]tap 8.2 ppb 3.8 ppb 30% Partial LSL (Pb/Cu) (7,090) 1.9 ppb Post-war (Cu) [ ] (28,300) 0.4 ppb 55% (52,000) 0.4 ppb New home (Cu) [ ] # of children

19 Expected BLL increase as a function of tap water lead concentration, given typical Canadian levels of Pb in dust/food/air (IEUBK modelling by E.Deshommes, Ecole Polyt.)

20 Potential lead exposure pattern in municipal water supply City of Ottawa (population 875,000; 10.8% <9 yrs old) Corrosion control with ph=9.2 (summer) 15% Older homes (Pb) [ ] 50% 50% (Pb/Pb) 90% 10% BAD normal (710) (6,380) [Pb]tap 8.2 ppb 3.8 ppb +BLL +1.3 µg/dl +0.6 µg/dl 30% Partial LSL (Pb/Cu) (7,090) 1.9 ppb +0.3 µg/dl Post-war (Cu) [ ] (28,300) 0.4 ppb µg/dl 55% (52,000) 0.4 ppb µg/dl New home (Cu) [ ] # of children

21 Potential lead exposure pattern in municipal water supply City of Ottawa (population 875,000; 10.8% <9 yrs old) Corrosion control w. phosphate at ph=7.5 (summer) 15% Older homes (Pb) [ ] 50% 50% (Pb/Pb) 90% 10% BAD normal (710) (6,380) [Pb]tap 1.9 ppb 1.4 ppb +BLL +0.3 µg/dl +0.2 µg/dl 30% Partial LSL (Pb/Cu) (7,090) 0.6 ppb µg/dl Post-war (Cu) [ ] (28,300) 0.2 ppb µg/dl 55% (52,000) 0.2 ppb µg/dl New home (Cu) [ ] # of children

22 Potential lead exposure pattern in municipal water supply City of Ottawa (population 875,000; 10.8% <9 yrs old) Water supply with no corrosion control (ph=7.5) 15% Older homes (Pb) [ ] 50% 50% (Pb/Pb) 90% 10% BAD normal (710) (6,380) [Pb]tap +BLL 27.7 ppb 19.8 ppb +4.0 µg/dl +3.0 µg/dl 30% Partial LSL (Pb/Cu) (7,090) 10.9 ppb +1.7 µg/dl Post-war (Cu) [ ] (28,300) 0.4 ppb µg/dl 55% (52,000) 0.4 ppb µg/dl New home (Cu) [ ] # of children

23 Environmental sources of lead

24 Lead in Soil conc. (µg/g) Environmental sources of lead 350 Lead concentration in soil ( ) Health Canada State of Science report,

25 Environmental sources of lead

26 Environmental sources of lead

27 Blood lead levels (BLL) observed in recent epidemiological studies or health surveys BLL level (µg/dl) Location Year Age No. in study Study 1.50 (GM) USA years n=817 NHANES, (GM) Hamilton years n=643 Hamilton Public Health, (GM) St.John s, NFLD years n=~300 St.John s Public Health 1.35 (GM) Montreal years n=306 Levallois et al., (GM) Canada years n/a Statistics Canada, 2013

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29 Estimated BLL contribution from tap water & %homes in Ottawa +1.3 BLL +0.6 BLL 1% +0.3 BLL 7% 7% BLL <1% BLL 85%

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33 Importance of flushing tap for homes with bad LSL s? Lead conc. ppb ppb ppb Flowing Litre-1 Litre-2 Litre-3 Litre-4

34 Use of in-home filters to reduce lead (4) store-bought carafe-style filters being tested (1 certified for lead removal) cost approximately $15 - $35 harvested water from home with LSL = 4-7 µg/l twice per week, pour 2 Litres through each filter (sample 2 nd litre)

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36 Typical lead concentrations after filter <0.2 ppb <1 ppb 1-2 ppb <1.5 ppb Zero water: NSF certified for Pb removal carafe style pour-through filters reduce lead concentrations by 85 95% +3 months of testing and still performing well >80 Litres processed so far cost: $20-30

37 Questions, ideas, or comments?