Proposed Updated Guideline for Lead. France Lemieux Water and Air Quality Bureau Health Canada CWWA Window on Ottawa June 6, 2017 Ottawa, ON

Transcription

1 Proposed Updated Guideline for Lead France Lemieux Water and Air Quality Bureau Health Canada CWWA Window on Ottawa June 6, 2017 Ottawa, ON

2 Proposed Guideline Proposed Maximum acceptable concentration (MAC) of mg/l (5 ppb) (at the tap) Reduces risk and considers most recent health effects information Previous MAC (10 ppb) after flushing (1992) Chronic effects for 2-yr-old child; no longer considered protective Flushed sample assesses lead in distribution system; not related to exposure Specifically addresses exposure from drinking water: Factors affecting exposure Sampling/monitoring to assess typical exposure to lead Lead variability (particulate/dissolved) 2

3 Background Lead internationally accepted as non-threshold toxicant by many agencies (U.S. EPA, CDC, Health Canada) Lead exposure is associated with many health effects in humans, including: Developmental neurotoxicity; increases in systolic blood pressure; decreased kidney function; reduced cognition; reproductive effects; cancer; Decreased IQ is considered the critical effect: Strongest evidence for a causal effect Children were affected at the lowest blood lead levels studied 3

4 Exposure Generally, lead levels in the environment and in consumer products have significantly declined Lead service lines can contribute at least 50 75% of lead in drinking water Leaded brass and lead solder can also be important sources of lead in drinking water Lead levels can be highly variable and depend on number of factors Lead in drinking water needs to be measured at the tap 4

5 Sampling considerations Different sampling protocols achieve different objectives Some may be able to achieve more than one objective Sampling protocol selected depends on objective Exposure (30-min or Random Daytime) Investigative/diagnostic (sequential) Treatment performance (stagnation) Compliance (depends on compliance objective) Sampling protocol needs to capture exposure Variability needs to be considered because exposure varies Total lead dissolved and particulate fractions 5

6 Lead variability Many factors affect lead release Typically differ for particulate vs. dissolved Particulate lead release is random and mostly unpredictable Dissolved lead release is reasonably well characterized Dissolved lead release Largely dependent on water quality Also on surface area of lead surface (pipe length, diameter); Stagnation time of water Particulate lead release influenced by Physical disturbances (hydrant flushing, road work, etc.) LSL replacement (full or partial) Galvanic corrosion Hydraulic disturbances and transport of particles 6

7 Particulate lead Usually defined as > 0.45 µm Increases with stagnation, flow rate, galvanic corrosion Difficult to predict Can be bioaccessible Can be the main form of lead Linked to lead spikes up to 22,000 µg/l measured in large buildings One single aerator TOTAL PB = SOLUBLE PB + PARTICULATE PB Source: Deshommes et al.,

8 Correlation between particulate lead and metals Metals can accumulate on top of iron and lead in distribution system Iron and manganese scales can act as sink for lead Release of Fe and Mn scales can occur after full or partial LSL replacement Increased particulate lead release Red water events result in release of metals such as lead Need to monitor these events Need to assess total lead concentration Sample preparation is key 8

9 Sampling results What does a sample result tell you? Depends on how it was taken. 6 hours first and second draw 30 minutes first and second draw 5 minutes fully flushed samples Random daytime (RDT) Profiling sampling after 30 min and 6 hour stagnation 9

10 Sampling Impact of stagnation time e.g. Repeated sampling in 1 household with a full LSL over 1 year, 2L samples, no corrosion control Total Lead Pb concentration in µg/l - µg/l Mean Min-Max N=10 sampling events ph 7.8±0.1, Temperature 9.5±9 C Alk 93±14 mgcaco 3 /L 11±8% particulate Pb 5 min flushing 30 min stagnation 6 hr stagnation (2L) (2L) (6L profile) Source: 10

11 Exposure sampling Composite proportional sampling representative of average weekly exposure Sampling studies undertaken by the European Commission in the UK, France and the Netherlands Compared composite proportional sampling to: Fully Flushed (FF); Random Daytime (RDT) and; 30 minute stagnation (30MS) 11

12 Conclusions of sampling studies Fully flushed protocol not representative of average exposure 30MS representative of average exposure and reproducible Underestimates exposure Representative of average inter-use stagnation time RDT representative of average exposure but less reproducible (need more samples) Captures variability Over-estimates exposure (more conservative) Representative of average inter-use stagnation time 12

13 Monitoring Needs to achieve objective (assess exposure) Needs to address residential sites Single family homes Multi-dwelling residences Needs to consider practicality/customer acceptability Should include buildings and schools Capture vulnerable population Different challenges (fittings, faucets, bubblers) Should address variability, building type, seasonal differences, occupancy/water use Target high risk areas/zones 13

14 Sampling Sampling type, locations and number 30MS or RDT (30 MS typically used for sentinel sites) In areas known or likely to have lead service lines or that have older buildings Homes with LSLs (full or partial) should be prioritized Include zones supplied by potentially corrosive water (e.g., dead ends when chloraminating) and consecutive systems Protocol for large buildings and schools Difficult to assess representative sample, so RDT recommended approach Needs be practical/realistic for large buildings and schools 14

15 Thank you! 15

16 Sampling Impact of particulate lead e.g. Repeated sampling in one household (6hr stagnation) Source: 16

17 Sampling Impact of the volume collected e.g. 30min profile sampling in one household Pb concentration - µg/l Premise plumbing Pb Cu Main 1 st L 2 nd L 3 rd L 4 th L 5 th L 6 th L 7 th L 8 th L Sequential liters of water collected at the tap Source: 17

18 Strategies to reduce lead Full lead service line replacement is best approach Partial lead service line replacement reduces lead May cause release of lead for several months Reduction may not mirror percentage of line removal Corrosion control May not be sufficient to reduce lead concentrations when water is supplied through a lead service line More low lead materials (comply with NSF 372 and NSF 61) for plumbing and distribution systems available Filters work well but are still a temporary measure 18

19 Acknowlegements Michèle Prévost, École Polytechnique Élise Deshommes, École Polytechnique Julie Bourdon-Lacombe, Health Canada 19