Evaluation of proposed new HBV for lead in drinking water Ian Douglas July, 2016

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1 Evaluation of proposed new HBV for lead in drinking water Ian Douglas July, 2016 Background Health Canada has recently completed a new risk assessment for lead in drinking water, currently prepared as a DRAFT for public comment. The proposed MAC lead concentration has been reduced from 10 µg/l to 5 µg/l with ALARA, based on increasing concerns about adverse neurological effects in children. Numerous research studies have observed children with measurable cognitive and neurobehavioural deficits at blood-lead levels (BLL) below the current BLL action limit of 5 µg/dl (US Centre for Disease Control). As a result of these and other concerns about lead toxicity, the American Academy of Pediatrics (2016) has recommended an even lower drinking water action limit of 1 µg/l for school water supplies. Given that IQ and other neuro-behavioural effects (e.g. ADHD) are considered to be important social determinants of health, it is important that these issues be carefully and thoroughly considered. However, since the implications of a lower MAC will be highly significant for many drinking water utilities in Canada, it is equally important that the health risk/benefit evidence is clearly understood and communicated. In many ways, the risk assessment itself will inform the type of actions taken by water utilities and public health professionals to achieve lower health targets and protect consumers. Purpose of document The primary focus of this briefing note is the health impact of lead and the relative contribution of drinking water to overall lead exposure. Specifically, the discussion paper attempts to address the following key questions: a) What levels of BLL (blood lead) are associated with adverse neurological effects in children? b) How does the lead contribution from drinking water compare to other environmental sources? c) What is the relationship between drinking water lead concentrations and BLL? d) Analytical and treatment considerations or limitations? The briefing note is intended to catalyze further discussion and to identify any additional knowledge gaps that need to be filled in order to provide sound advice on the risk management of lead in drinking water. 1 Page

2 a) BLL and associated neurological effects The proposed Health Canada risk assessment cites several studies that found adverse neurological effects associated with elevated BLL values, with BLL being considered an important biomarker of recent lead exposure. Adults for adults, numerous studies involving lead industry workers showed cognitive and neurological effects for BLLs in the range of µg/dl. A few of the cited studies also observed adverse neurological effects at BLLs below 10 µg/dl but the associations were weak and included studies that did not observe any adverse effects in this range. Children for children, several research studies indicate adverse health effects, even at low BLLs (<5 µg/dl). Epidemiological studies have associated BLL with adverse neuro-developmental effects including neuromotor function, poor academic achievement, reading scores, math skills, abnormal behaviour, decreased attention, and auditory/visual function. Studies observing adverse effects on attention deficit behaviours have been associated with BLLs below 5 µg/dl. One study (Braun et al., 2006) found that BLLs exceeding 2 µg/dl were associated with a 4.1-fold increase in the risk of ADHD. Another study (Froehlich et al., 2009) found that BLLs above 1.3 µg/dl were associated with a 2.3-fold increase in ADHD. Another study found that a 1 µg/dl increase in BLL (children aged 3-5 years) was associated with increases in teacher-reported behavioural problems (emotional reactivity, anxiety, development). The greatest weight of evidence has been shown for IQ deficit effects associated with BLLs. 12 cohorts were reviewed for the Health Canada document, four of which found strong evidence of decreased IQ, although it is important to note that these were for highly exposed individuals. One cohort observed adverse effects on IQ at the lowest peak BLL of 2.1 µg/dl (Jusko et al., 2008). Six of the cohorts found an association but did not reach statistical significance. The foundational study cited is the Lanphear et al. (2005) meta-study which analyzed 7 cohort groups involving 1333 subjects. Concurrent BLLs were associated with decreased IQ with a BLL increase from 2.4 to 10.0 µg/dl (+7.6) associated with a 3.9- point decrease in IQ. It should be noted however that the median BLL levels in the 7 cohort groups were quite high: 7.6 µg/dl (Boston), 11.7 µg/dl (Cincinnati), 14.5 µg/dl (Cleveland), 10.6 µg/dl (Mexico), 18.6 µg/dl (Port Pirie, Australia), 5.5 µg/dl (Rochester), and 15.8 µg/dl (Yugoslavia). A statistical reworking of the data set (EFSA, 2013) used linear regression to determine that a BLL increase of 1.2 µg/dl was associated with an IQ decrease of 1 point or 1%. If this conclusion is valid, it would suggest that ingestion of tap water that raises the BLL from 1.0 to 2.2 µg/dl, for example, would result in a potential IQ deficit of 1-point. While there is still great uncertainty with this finding, it does provide an interesting point of reference for the 2 Page

3 relationship between tap water lead concentration and measurable health impact. It is also important to note that given the test variability of IQ, a difference of 1 IQ point in a test population would be difficult to discern and probably represents a threshold of measurement. The Health Canada review document does not cite any studies that showed adverse neurological effects at BLLs below 2 µg/dl. Instead, the bench-mark dose determined by EFSA (2013) was based on extrapolation of IQ deficits associated with high BLLs in the range of 10 µg/dl. Nonetheless, the weight of evidence suggests that adverse neurological effects are likely to occur for BLLs <5 µg/dl, and possibly as low as 1-2 µg/dl. In the absence of a more comprehensive review, the EFSA (2013) benchmark statement that a BLL increase of 1.2 µg/dl is associated with an IQ decrease of 1 point provides a reasonable point of departure for assessing potential drinking water impacts. Future studies of neuro-behavioural and cognitive function will hopefully determine if low BLLs in the range of 1-2 µg/dl are associated with negative effects. 3 Page

4 b) Lead from drinking water vs. other environmental sources Infants are born with measurable amounts of lead in their blood arising from maternal exposure. As children develop they are exposed to several environmental sources of lead including household dust, soil, air, food, and water. Exposures vary with age due to differences such as body weight, food sources, breast-feeding, mouthing behaviours, amount of water ingested per day, etc. The following graph shows the estimated intake of lead (µg/day) for a 5-year old Canadian child from various environmental sources. The graph compares a child living in an older home (pre s) with a lead water service line to the case of a newer home (eg. post-1980 s) with a copper or plastic water service. The lead concentrations for air, soil, dust, and food are average values derived from the most recent data available from Health Canada. 25 Estimated Daily Lead Intake of Lead From All Sources For A 5 Year Old Air, Food and Dirt Data From Health Canada State of the Science 2013 Report except New Home with Copper Service, Dust from P.E.Rassmussen 2011 Canadian House Dust Study Lead Intake (µg/day) Water Dirt Dust Food Air Contribution from Air is 0.01 µg/d LSL Home No Corrosion Control (20 µg/l) LSL Home Current MAC (10 µg/l) LSL Home Proposed MAC (5 µg/l) LSL Home At 1 µg/l New Home (0.3 µg/l) The graph indicates quite clearly that drinking water can be a moderate source of lead exposure. Other environmental sources that were historically quite high (soil, food, air) have declined dramatically in recent decades such that water has become a more prominent contribution to overall lead intake. The graph illustrates that a reduction in a drinking water MAC from 10 to 5 µg/l would result in a moderate decrease in overall lead intake. It is apparent from the graph that once drinking water lead is reduced to a low level (approximately 1 µg/l), household dust and food are the most significant 4 Page

5 source of lead. A child living in a newer home with a copper or plastic water service connection would experience a negligible amount of lead from tap water. For example, in the City of Ottawa, when testing was conducted in 914 homes with a copper service pipe, the average lead concentration was found to be <1 µg/l (0.35 µg/l in flowing sample). It is possible through a number of mitigation measures (corrosion control, flushing, filter) to achieve a tap water lead concentration of 1 µg/l, even in older homes with LSL service pipes. This means that it is possible for all children in a given community to achieve minimal lead exposure from tap water regardless of the age of the house or socio-economic status. Similar calculations of daily lead intake for a 2-year old infant are shown in the graph below illustrating very similar trends. 25 Estimated Daily Intake of Lead From All Sources For A 2 Year Old Air, Food and Dirt Data From Health Canada State of the Science 2013 Report except New Home with Copper Service, Dust from P.E.Rassmussen 2011 Canadian House Dust Study Water Dirt Dust Food Air Lead Intake (µg/day) Contribution from Air is µg/d LSL Home No Corrosion Control (20 µg/l) LSL Home Current MAC (10 µg/l) LSL Home Proposed MAC (5 µg/l) LSL Home At 1 µg/l New Home (0.3 µg/l) Many environmental sources of lead have decreased significantly over the last few decades, most notably from the elimination of lead in gasoline. As an illustration, the following graphs show steady decline in lead concentrations for air and soil samples in Canada. 5 Page

6 Long term trends for Canadian lead concentrations in soil, food, & air Lead concentration in soil ( ) Health Canada State of Science report, 2013 Lead in Soil conc. (µg/g) Accordingly, BLL levels have been steadily decreasing from approximately µg/dl during the 1960 s and 1970 s to approximately 1 µg/dl for children in Canada. The 6 Page

7 following graph shows the sharp decrease (data cited in a 2007 Quebec Environment Report). Blood-lead concentration in children <6yrs in Canada and United States 20 Blood lead conc. (ug/dl) Canada United States 2 0 Ottawa study (2000) Year Based on a few recent Canadian studies, childhood BLL levels are now typically in the range of (µg/dl). The table below shows geometric mean BLL values cited in a few recent health studies. The data indicates low BLL values in Canadian children and continuing gradual decline over recent years. 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, Page

8 c) Relationship between DWL concentration and BLLs There appears to be a direct relationship between drinking water lead (DWL) concentrations and the resulting blood lead levels (BLL). A child who regularly consumes tap water at elevated lead concentrations will experience an increase in BLL above background. The evidence for this comes from two sources: (i) results of IEUBK modelling for children 0-7 years, and (ii) epidemiological evidence measuring BLLs as a function of various tap water concentrations. (i) the IEUBK model was developed by the US-EPA based on bio-kinetic knowledge of the absorption and uptake of lead from various sources. The model was calibrated on the basis of several case studies of lead exposure arising from tap water (Scotland) and infant formula (Japan). The IEUBK model was also validated using Canadian data from a recent Montreal epidemiological study of BLL levels. Using the model, Ecole Polytechnique (2015) prepared the important graph below showing estimated BLL levels in children from 0 7 years. In this case, drinking water lead concentrations were varied while keeping other environmental sources constant (air, food, soil, & dust): The graph clearly shows the effect of DWL on BLL levels, although the BLL trend varies somewhat over the age range due to changes in exposure patterns, body 8 P age

9 weight, consumption, etc. For each of the 0-7 year profiles, a geometric mean BLL value can be calculated. To explore the relationship between tap water and resultant blood-lead concentrations, the geometric BLL values were plotted as a function of drinking water lead concentrations (DWL): Predicted BLL levels age (0.5-7 yrs) vs. tap water concentrations IEUBK model results - E.Deshommes, Ecole Polytechnique (2015) tap water = lead conc. (µg/l) with variable intake L/day by age; absorption fraction of 50% dust/soil = intake amounts by IEUBK default values (g/d) & Rasmussen study of soil/dust in Canadian homes air = µg/m3 (Health Canada, 2011); ventilation rate = 2 7 m3/d variable with age; lung absorption = 32% food = dietary intake of µg/day, depending on age Estimated geometric mean BLL for 0 7 yrs (µg/dl) vs. tap water Pb conc. E.Polytechnique (2016) using IEUBK model (US_EPA) Estimated BLL concentration µg/dl y = x x Tap water lead concentration (µg/l) For risk assessment and regulatory purposes, the lower end of the graph is most relevant. Accordingly, the low end of the graph has been expanded in the graph below. The graph indicates a direct relationship between DWL and BLL, at least for this range of exposure. For a child consuming tap water with 0 µg/l, the background BLL is estimated to be 1.15 µg/dl, attributable to other environmental sources such as food, dust, air, and maternal BLL. This background BLL level predicted by the IEUBK model is reasonably comparable to levels observed in recent Canadian epidemiological studies (Montreal, Hamilton). As the assumed DWL concentration increases, the BLL level increases accordingly. 9 Page

10 Estimated geometric mean BLL for 0 7 yrs (µg/dl) vs. tap water Pb conc. E.Polytechnique (2016) using IEUBK model (US_EPA) 5.0 Estimated BLL concentration µg/dl BLL=2.70 BLL=1.94 y = x x BLL=1.31 BLL=1.15 (tap Pb=0) µg/l 1 µg/l 10 µg/l Tap water lead concentration (µg/l) Using this graph, it is interesting to compare the impact of tap water at concentrations of 10, 5, and 1 µg/l. Based on the model, a child routinely consuming water with a lead concentration of 10, 5, and 1 µg/l would have a predicted BLL of 2.70, 1.94, and 1.31 µg/dl respectively. At the current MAC concentration of 10 µg/l, a BLL of 2.70 µg/dl represents a net increase of +1.5 µg/dl above background. If the EFSA determination is taken to be true, this would result in a potential IQ deficit of 1.25 points on average. Similarly, it follows that a lowering of the regulatory MAC to a value of 5 µg/l would result in a BLL increase of +0.8 µg/dl which represents a potential IQ deficit of 0.7 points. At the low end of the scale, a tap water concentration of 1 µg/l would result in a BLL increase of only µg/dl, representing a potential IQ reduction of 0.1 points. It is arguable that this level of effect would be indiscernable by IQ testing and could be considered a de minimus level of risk. An observation of great concern is the fact that several Canadian cities have routinely measured summer tap water lead concentrations in the range of µg/l, which 10 Page

11 might be resulting in BLL levels in the range of 4.15 µg/dl which have the potential to cause a deficit in the range of 3 IQ points. The neurological studies cited in the Health Canada document indicated adverse health effects for BLLs below 5 µg/dl and perhaps as low as µg/dl. If a risk threshold value of 1.5 µg/dl is assumed for discussion purposes, the shaded area of the graph indicates a region of potential adverse impact. In this context, the adoption of a 5 µg/l drinking water guideline certainly reduces risk, but a lower target of 1 µg/l might be required to arrive in the safe or negligible zone for neurological impacts in children. (ii) Several epidemiological studies have been conducted in recent years in St. John s (NFLD), Saint John (NB), Hamilton, and Montreal to determine the level of BLL observed in children, and to evaluate the impact of tap water lead concentration on observed BLLs. The most recent study was conducted using n=306 children (age 1-5 years) in an older section of Montreal during winter conditions. The geometric mean BLL was 1.35 µg/dl (range µg/dl). Although tap water lead concentrations were relatively low during the winter study conditions (1.60 µg/l geometric mean), the study found that BLL levels were elevated above the 75 th percentile value (1.78 µg/dl) when the mean water concentration was above 3.3 µg/l. Similarly, the City of Hamilton study found that average BLL levels increased with lead concentrations in the tap water (see table below). These findings indicate that exposures to tap water, even at low concentrations, can result in measurable increase in BLL. Impact of DWL on BLL for City of Hamilton study ( ) Tap water lead concentration (µg/l) Blood lead level (µg/dl) < > Page

12 d) Analytical and treatment considerations Analytical The Health Canada document cites 5 µg/l as a practical quantitation limit for lead in drinking water, as referenced by the US-EPA. However, common experience measuring lead at several commercial laboratories shows MDLs in the range of µg/l. These levels of detection are well below the proposed MAC and represent 1/50 th or 1/500 th of the action level. In fact, the recent Montreal study (2014) used a commercial accredited laboratory (Maxxam Ltd.) and cited a detection limit of 0.01µg/L with a quantitation limit of µg/l. Quality control samples were regularly analyzed and the correlation coefficient for duplicate samples was Clearly, analytical methods do not pose a limitation for setting a new MAC standard for lead. Treatment & other lead reduction measures Older homes that are served by lead service pipes (LSL) result in the highest tap water lead concentrations in a water distribution system. For these cases, there are several municipal and homeowner actions that could be used to effectively reduce lead concentrations: 1) treatment - corrosion control using ph adjustment 2) treatment corrosion control using phosphate addition 3) carefully flushing of household plumbing (eg. 1-2 minutes) 4) use of an in-home water filter (NSF or carafe-style filter) 5) installation of certified non-lead tap fixtures 6) replacement of the LSL Treatment due to the solubility of lead, summer warm temperature conditions pose the greatest risk of elevated lead in drinking water. In the City of Ottawa, extensive pilot and full-scale studies have shown that a treated water ph of 7.5 would result in flowing lead concentrations in the range of µg/l, and higher for stagnation samples representing the LSL pipe. By adjusting the treated water ph to 9.2 units the resulting lead concentration averages 2.5 µg/l for fully flushed samples in summer. In Ottawa, the chemical cost (NaOH) to raise the ph to 9.2 units is approximately $500,000 per year (population=870,000) or a per capita cost of $0.57/year. In water systems with higher source water alkalinity, this treatment option would be considerably higher since it would require more chemical to increase ph. Alternatively, the addition of 1 mgp/l phosphate for corrosion control is estimated to reduce flowing and stagnant lead concentrations to approximately 1-2 µg/l, at a comparable operating cost. In Ottawa, a one-time capital cost in the range of $5 Million would be required to install storage tanks and related feed equipment in both treatment plants. 12 Page

13 Tap flushing household flushing is very effective and inexpensive for reducing lead exposure from tap water. This usually consists of 1-2 minutes of full flow (4-6 L/min) at the kitchen tap prior to using water for consumption or cooking. If this were done twice per day for 2 minutes, the cost of water would amount to $0.04 or 4 cents/day. City of Ottawa data from LSL homes shows that lead levels can be reduced by 50-75% using this technique. Filtration the use of a carafe-style filter (eg. BRITA) is able to further reduce lead concentrations by 40-80%, based on tests performed in approximately 50 homes. The use of an NSF-certified cartridge filter designed for lead removal can lower lead concentrations to <1 µg/l. LSL replacement in older (pre-1955) homes, replacement of the entire LSL pipe with copper or plastic piping can reduce or eliminate tap water lead concentrations. In these cases, the lead concentration is typically reduced to <1 µg/l. However, this typically requires a cost of $2,000 - $4,000 to replace the private portion of the LSL, and a higher cost to the municipality to replace the public portion of the LSL. In addition, there would be significant disruption to city traffic and other utilities to conduct the work. In Ottawa, there are an estimated 30,000 LSL services still in place which amounts to well over $100 Million in potential construction costs. 13 Page