Appendix A Revised Emission Factors for Mercury N.Z Data Ron Pilgrim & Murray Thomson 1 December 2015

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1 Appendix A Revised Emission Factors for Mercury N.Z Data Ron Pilgrim & Murray Thomson 1 December Please provide up-to-date population data (publically available from Statistics New Zealand) and New Zealand dental data (should be available from the New Zealand Dental Association) justifying the assumption of an average 1.55 grams of mercury per person. RPC Response Background I had for many years assumed an average rate of mercury emission from cremation in New Zealand of 2.1 g/cremation which is the mean of the two N.Z. estimates (1.53 and 2.61g/body by Cutress and Cutress ). I also believed that the average rate of emission of mercury is somewhat lower now than estimated which, if correct, makes the 2.1 g/cremation emission factor conservative. Observations by Harvey-Bowler Limited, Levin, during the period 1 February to 30 March 2001 suggested a lower rate of amalgam restorations (averaged 2.05 fillings per person or 1.23 g Hg/body based on 0.60 g hg/filling) 3 which may reflect a higher average age at death for the Levin population. I was also advised in that in New Zealand there has been a trend of reduction of amalgam use. (This was based on better dental health, hence lower requirements of fillings with approximately 30% reduction over the past 20 years ending In addition, in private practices dentists are using alternatives to amalgam in some cases but in the public sector only amalgam fillings were used for restorations.) The US EPA (1997) emission factor for mercury (3.29E -03 lb/cremation) 5 is equivalent to an average rate of mercury emission of 1.5 g per cremation. This average rate of emission is slightly lower than what I believed was the average in New Zealand, and this may be due to better dental hygiene and/or the use of alternative restoration materials to amalgam in the USA. A statistical analysis of a large volume of USA dental data was carried out by The Bay Area Air Quality Management Division (the Bay Area includes the City of San Francisco). It was estimated that the average rate of emission of mercury per cremation was lb (1.54 g). For the estimation of an acute short term exposure all of the mercury was assumed to be vaporised during the first hour of cremation. 6 I used this average rate of mercury emission from cremation for the Bledisloe N.Z. Ltd. proposed new cremator in Hastings. For the assessment of effects on the environment for the Hastings District Council s replacement cremator (see Section of AEE dated 30 September 2015) I used an average emission of 1.55 g ( kg)/cremation as an hourly average, and assumed all of the mercury is volatilised and discharged to air during the first hour of cremation. The rate of emission of mercury of 1.55 g/cremation is the average emission factor for mercury presented in the Australian NPI Emission 1 Cutress et al. Adult Oral Health and Attitudes to Dentistry in New Zealand. Medical Research Council of New Zealand, Wellington Cutress, T.W. Dental Amalgam and Human Health - Current Situation. Report to the N.Z. Ministry of Health, January Observations by Harvey-Bowler Limited, Levin, during the period 1 February and 30 March 2001 suggested a lower rate of amalgam restorations (2.05 per person). 4 Personal Communication: Mira Chakraborty (KML) and Peter Hunter, Ministry of Health, 22 January US EPA. Locating and Estimating Air Emissions from Sources of Mercury and Mercury Compounds. EPA- 454/R December Bay Area Air Quality Management District. Mercury Emissions from the Cremation of Human Remains. September (Supporting documentation for an updated mercury emission factor in the BAAQMD Permit Handbook chapter for crematories.) Postal Address: 39 Wairere Road, Belmont, Lower Hutt Telephone: (04) Cell Phone: (0275) Fax: (04) ronpilgrimconsulting@gmail.com

2 Estimation Technique Manual for Crematoria (2011) 7 calculated from data from the Australian National Survey of Oral Health This emission factor is essentially the same as the Californian Bay Area Air Quality Management Division s 2012 estimated average rate of emission of mercury from cremation. Information for this Assessment Information to address this request was obtained from the following sources. N.Z. Dental Association (Hugh Trengrove) in respect to sources of published information and expert opinions. N.Z. Ministry of Health. New Zealand Mortality Statistics: 1950 to 2010 (Provisional) by age groups (year 2009 corresponds to the Ministry of Health s 2009 oral health survey). This Table is included in Appendix B. N.Z. Ministry of Health. Our Oral Health: Key Findings of the 2009 New Zealand Oral Health Survey, in particular Figure 5 (prevalence of complete tooth loss (edentulism) among adults aged 18 and over by age group), Figure 13 (mean number of filled teeth among dentate adults aged 18 and over by age group), and Figure 66 (mean number of filled coronal surfaces per person among New Zealand and Australian dentate adults aged 15 and over by age group). These figures are included in Appendix B. Information from Terry Brady Consulting, Auckland, reporting the expert opinion in January 2001 of the former Emeritus Professor James Hood, School of Dentistry, University of Otago, in respect to the average size of amalgam restorations, and Terry Brady s spreadsheet calculations of mass of mercury per average restoration. Expert opinions from Professor Murray Thomson, Professor of Dental Epidemiology and Public Health, and Head, Department of Oral Sciences, Faculty of Dentistry, University of Otago. Prof. Thomson s opinions related to methodology to estimate the average mercury content of restorations in New Zealand by age group; the applicability of Prof. Hood s average amalgam filling size to the 2009 situation; estimates of the number of amalgam restorations and percentage of amalgam restorations to total restorations by age group; and general advice. Prof. Thomson s estimates are based his clinical experience and experience in examining people in a number of surveys over the years, and on his reanalysis of the 2009 national survey data-set. Method of Calculation of Average Mercury Content of Amalgam Restorations The calculation of estimated average mercury content of amalgam restorations (fillings) for the 55 to 75 year plus age group used the following information: average diameter and depth of fillings of 4 mm and 2.5 mm respectively (J. Hood, 2001); volume of the average filling cm 3 ; density of mercury of g/cm 3 at room temperature; and the mass of the average amalgam filling if composed entirely of mercury (of g) multiplied by the average mercury content of amalgam fillings (assumed to be 50%). The mercury content of the average amalgam filling based on J. Hood (2001) average filling size is g (rounded to 0.21 g). In respect to the average mercury content of fillings for the 15 to 54 age group, Prof. Thomson believes Prof. Hood s estimate for the average size of a filling is likely to be an over-estimate by modern standards. The typical mercury content of amalgam fillings is likely to be progressively lower in the younger age groups because of more conservative tooth preparations (that is, less drilling out of tooth tissue). Consequently, an estimated mercury content of 0.10 g/filling was provided based on an average filling size of 3 mm diameter and 2 mm deep. This gives a volume of cm 3 which is 7 Australian Government. National Pollutant Inventory Emission Estimation Technique Manual for Crematoria. Version 1, March Appendix B, page

3 slightly less than half of that based on Prof. Hood s estimated average amalgam filling size, and ghg/filling (rounded to 0.10 g/filling). Upper and Lower Bounds and Midpoint Prof. Thomson also comments that because most of the restorations in the older age groups are likely to be multi-surface fillings, using the number of filled surfaces is likely to lead to an over-estimate of their mercury content. On the other hand, using the number of filled teeth only is likely to lead to a systematic under-estimation, especially in the older age groups. Consequently, he suggested using the surface-based and tooth-based estimates as upper and lower bounds for the estimates, especially for the older age groups. In addition, using the midpoint between upper and lower bounds for assessment purposes would not be unreasonable, especially since these data are estimates. Calculation to Estimate the Average Mercury Content of Amalgam Fillings Calculations to estimate the average mercury content of amalgam fillings per person by age group as upper bound, lower bound, and midpoint consist of the following steps: Estimate the percentage of dentate (having one or more teeth) persons by subtracting percentage of edentate (complete tooth loss) provided in Figure 5 of the N.Z. oral health survey (2009) (for example, for the 75 years + age group, 100% - 40% = 60% dentate (0.60); For upper bound estimates, the number of filled coronal surfaces from Figure 66 of the N.Z. oral health survey (2009) as an estimate of the average number of fillings per person (for example, for the 75+ age group, 37.3 per person on average); For lower bound estimates, the number of filled teeth from Figure 13 of the N.Z. oral health survey (2009) as an estimate of the average number of fillings per person (for example, for the 75+ age group 10.6 per person on average); Estimated percentage of amalgam fillings to total fillings provided by M. Thomson (for the 45 to 75+ age group, 75% (0.75), for the 25 to 44 age groups 50% (0.50), and for the 15 to 24 age group 40% (0.40)); and Estimated average mercury content of amalgam fillings of 0.21 g/filling for the 55 to 75+ age group, and 0.10 g/filling for the 15 to 54 years age groups. For example for the 75+ age group using the number of filled coronal surfaces: 0.60 x 33.6 x 0.75 x 0.21 ghg/filling = 3.17 (3.2) g Hg/person on average. Tables Table 8 presents estimated dental amalgam mercury per person based on filled coronal surfaces by age group as upper bound estimates, and Table 9 is based on number of filled teeth as lower bound estimates. The age group-weighted mean for upper bound and lower bound estimates are also provided. 92

4 Table 8: Estimated Dental Amalgam Mercury per Person based on Filled Coronal Surfaces by Age Group Upper Bound Age Group (years) Percentage Dentate No. Filled Coronal Surfaces Percentage Amalgam (Note 1 ) Mercury g/filling (Notes 2 & 3) Mean Dental Mercury g/person Mortality by Age Group (2009) % Mort. by Age Group (2009) (0.604) (0.75) 0.21 g , % 65 to (0.704) (0.75) 0.21 g , % 55 to (0.854) (0.75) 0.21 g , % 45 to (0.968) (0.75) 0.10 g , % 35 to (0.983) (0.50) 0.10 g to (1.00) (0.50) 0.10 g to 24 (18 24 yrs) 99.9 (0.999) (0.40) 0.10 g to 14 Insufficient data unknown [88] [0.30] Assume no amalgam fillings - Assumed nil Age groupweighted mean Note 1: Thomson Note 2: Hood Note 3: Thomson (3.3) = 29,083 n = 29, % 99.7% Table 9: Estimated Dental Amalgam Mercury per Person based on Filled Teeth by Age Group Lower Bound Age Group (years) Percentage Dentate No. Filled Teeth Percentage Amalgam (Note 1 ) Mercury g/filling (Notes 2 & 3) Mean Dental Mercury g/person Mortality by Age Group (2009) % Mort. by Age Group (2009) (0.604) (0.75) 0.21 g , % 65 to (0.704) (0.75) 0.21 g , % 55 to (0.854) (0.75) 0.21 g , % 45 to (0.968) (0.75) 0.10 g , % 35 to (0.983) (0.50) 0.10 g to (1.00) (0.50) 0.10 g to 24 (18 24 yrs) 99.9 (0.999) (18 24 yrs) (0.40) 0.10 g to 14 Insufficient data Unknown [88] [0.30] Assume no amalgam fillings - Assume Nil Age groupweighted mean Midpoint between Upper and Lower Bounds 1.07 (1.1) = 29,083 n = 29, % 99.7% The midpoint between upper and lower bounds based on the two age group-weighted means is (2.2) g mercury per person. 93

5 Appendix From: N.Z. Ministry of Health. New Zealand Mortality Statistics: 1950 to 2010 (Provisional) By age groups Page 5. From: N.Z. Ministry of Health. Our Oral Health: Key Findings of the 2009 New Zealand Oral Health Survey Figures 5, 13, and

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Consultation on proposed prescribed qualifications for the General Dental, Oral and Maxillofacial Surgery and Dental Technology Scopes of Practice

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