Human Health Risk Assessment

Transcription

1 Human Health Risk Assessment The difficulty in predicting postdevelopment fibre release Dr Richard Ogden Land Quality Management Ltd Tel: Full contact details at : Forthcoming asbestos events: CIRIA Conference Risk assessment and management of asbestos in made ground the conference 7 Oct 2015, Birmingham isplay.aspx?eventkey=e15513 Ciria Masterclass Asbestos from soil - quantitative risk assessment 8 Sep 2015 London isplay.aspx?eventkey=e

2 LQM and asbestos Authors (together with asbestos-experts from IOM) of the recent Ciria C733 Renowned knowledge of contaminated land assessment, management and remediation Track record of using detailed risk assessments to avoid unnecessary remediation saving public and private sector large sums of money Several projects relating to asbestos-containing soils (under planning and Part 2A) Soil risk assessment: The basics Exposure estimation: What is the anticipated exposure for the relevant land use/exposure scenario (residential, public park, BMX track, allotment etc.)? Risk estimation: Based on our toxicological knowledge, what level of risk to health does this exposure pose? Risk evaluation: Is this level of risk unacceptable given the uncertainty and assumptions in the assessment Air + Foodchain + Soil + = 2

3 Exposure estimation: Cumulative exposure The risk of asbestos-related cancer is dependant on cumulative exposure Normally calculated in fibre/ml.hours Estimated airborne fibre concentration (f/ml) multiplied by total exposure period (ie hours/year x number of years) If more than one activity could lead to exposure sum all activities (ie outdoor gardening, indoor track back). This is the difficult bit we will return to it later! Risk estimation: Epidemiological models Several exposure-risk models that predict lifetime excess cancer risk (ELCR) for cumulative exposures in f/ml.yrs, for example: Berman and Crump (B&C) 2008 Hodgson and Darnton 2000 Risk summaries in C733 Each model consists of a separate module for asbestosrelated lung cancers and mesotheliomas These models were generated from the number of cancers/deaths in people who were exposed to asbestos at work So are based on occupational years 40hrs x 48 weeks ~ 2000hrs So f/ml.hrs 2000hrs/yr ~f/ml.yrs 3

4 Risk estimation: Acceptable/unacceptable? Estimating the risk is easy but deciding if the risk is acceptable is not! We will do an example in a minute ELCR of 1:100,000 is generally considered the limit of minimal risk But how accurate was the estimated exposure? We will discuss the large uncertainties in the exposure estimation later These uncertainties need to be carefully considered when deciding what is an acceptable and unacceptable risk from asbestos-containing soils Risk evaluation: Example A child is exposed airborne crocidolite (0.001 fibres/ml) while indoors for 23 hours per day, 365 days per year, for the first 5 years of life. This is 1/10 th of the clearance indicator threshold (0.01 f/ml) 23 hrs/day 365 days/yr 5 yrs 42,000 hrs fibre/ml 42,000 hrs = 42 fibre/ml.hrs ~ 0.02 fibre/ml.yrs 4

5 Risk estimation: Mesothelioma risks Cumulative exposure (from age 30, over 5 yrs) Mesothelioma Lifetime Risk per 100,000 exposed Fibre/ml.years Crocidolite Amosite Chrysotile (Up to 2-fold uncertainty) 6500 (Up to 2-fold uncertainty) 200 (Up to 3-fold uncertainty) (Up to 2-fold uncertainty) 650 (Up to 2-fold uncertainty) 20 (Up to 3-fold uncertainty) (Highest arguable estimate 1500 lowest 250) (Highest arguable estimate 350 lowest 25)) (Highest arguable estimate 100 lowest 2)) 90 (Highest arguable estimate 300 lowest 15) 15 (Highest arguable estimate 80 lowest 2) 3 (highest20) 5 (Highest arguable estimate 20 lowest 1) (Highest 4) about 10 (Highest arguable estimate 55, lowest insignificant )) about 2 (highest arguable 15) Highest arguable becomes insignificant Highest arguable becomes insignificant Note that the above risks all apply to exposure startingat age 30. The cumulative exposure year is an occupational year assumed to be about 2000 hours. The cumulative exposures in column 1 can be converted tocumulative exposures infibre/ml.hoursby multiplyingby 2000; for example 0.01 fibre/ml.years = 20 fibre/ml.hours. (After Hodgson and Darnton (2000), table 11) Risk evaluation: Age adjustment factors for mesothelioma Age at which exposure commences Factor - to adjust risk from Table 14.1 (taking risk as persistingfor 60 years) (taking risk as persistingfor 80 years) (from paper to WATCH, developed by Hodgson and Darnton from the HEI model (HEI, 1991). 5

6 Risk evaluation: Example Estimated Cumulative Exposure was ~ 0.02 fibre/ml.yrs to crocidolite Mesothelioma risk: Risks for adults exposed to 0.01 fibre/ml.years of crocidolite is ~20 per 100,000 exposed. So the risks at 0.02 fibre/ml.years will twice this. The age adjustment factor (0-5yrs) is in 100,000 exposed. Risk evaluation: Lung cancer risk Cumulative exposure (from age 30, over 5 years) Lung cancer -Lifetime Risk per 100,000 exposed Fibre/ml.years Crocidolite Amosite Chrysotile (55000 to 25000) Same as for crocidolite 500, perhaps 3000, in exceptional circumstances (1000 to 2500) Same as for crocidolite 50, perhaps 300 in exceptional circumstances (20 to 250) Same as for crocidolite 2 perhaps 30, in exceptional circumstances (<1 to 25) Same as for crocidolite probably insignificant, perhaps 3, in exceptional circumstances to 3 (mesothelioma now dominant) Same as for crocidolite The cumulative exposure year is an occupational year assumed to be about 2000 hours. The cumulative exposures in column 1 can be converted tocumulative exposures infibre/ml.hoursby multiplyingby 2000; for example 0.01 fibre/ml.years = 20 fibre/ml.hours. (After Hodgson and Darnton (2000), table 11) 6

7 Risk evaluation: Example Estimated Cumulative Exposure was ~ 0.02 fibre/ml.yrs to crocidolite Calculated risk of mesothelioma 260 in 100,000 exposed Lung cancer risk: Risks for adults exposed to 0.01 fibre/ml.years of crocidolite is ~2 per 100,000 exposed. ~4 per 100,000 exposed No age adjustment factor is used for lung cancer Risks for smokers would be higher Excess lifetime cancer risk: per 100,000 exposed! Well above minimal risk levels of 1 per 100,000 Where is the uncertainty? Mainly, in exposure estimation Under what, if any, conditions are airborne fibres released from ACS in the UK? Weather conditions, depths, activities Desiccation on hard surfaces What, if any, is the relationship between soil and airborne fibre concentrations? How does it vary for different soils and made ground types? How much ACS be tracked back into homes and offices? How quickly will ACMs release free fibres into soils? Does AC in soil pose any risk? Internationally recognised problem 7

8 Cards on the table. Are SUBSTANTIAL concentrations of airborne fibres released from UK soils and made ground? We don t know Do asbestos-containing soils pose a MATERIAL risk in the UK? We don t know Do small amounts of asbestos (particularly chrysotile) in soils justify the current REMEDIATION costs? We don t know Can airborne fibres be released from soils? Theoretically, yes! Addison et al. (1988) proved that airborne fibres can be released vigorous disturbance dry soils (<10% moisture) Asbestos fibres not ACM We know that surface soils can dry out Especially where soil/mud desiccates on roads, paths and patios etc. QED airborne fibres could be released But there is no proof! Only ~48 measurements in 3 types of soil Very little real-world data Lot s of Airborne fibres rarely detected at construction sites How often do surface soils really dry out? What is the effect of vegetation/turf? QED would any exposure ever really be significant? 8

9 Are airborne fibres ever released from soil/made ground? But what about: Domestic gardens? School playing fields? Public parks? Etc. Very little data to prove that potential exposures can or cannot be significant 9

10 Existing air monitoring data Most current measurements (in the UK and elsewhere) are made during construction activities Are they representative of post development conditions? Health and safety provisions eg damping down in dry weather ( exposures) Large disturbance of soil ( exposures) Fibre types not determined Soil concentrations not well understood Measurements below LoD required by CAR (0.1 or 0.01 f/ml) usually assumed to be zero/acceptable/safe. But long-term exposures at, or below, these levels could pose unacceptable risks (especially for amphiboles) Dutch dataset: Lab vs field measurement? measurement conditions were frequently not well defined and the soil was often (made) damp, on account of which relatively favourable conditions (suppression of fibre emission) prevailed. Swartz et al (2003) Average airborne asbestos concentrations from several comparable measurements (symbols) in fibres/m3air and 95% confidence intervals (hyphens), from worst case simulation experiments ( ), from field measurements with friable () and bound () asbestos, as a function of asbestos concentration in soil. Straight lines represent the 95% intervals of all data. (After Swartjes & Tromp, 2008) 10

11 International questions (and possible solutions) These uncertainties are widely acknowledged Even in countries with published frameworks/ policy on asbestos-containing soils, including: Netherlands, Australia and USA Solutions and approaches: Ongoing research Development of novel soil sampling and testing methods that better represent potential fibre release rather than asbestos concentration Flexible policy frameworks Sharing of information USEPA: Activity-based sampling Preferred method at superfund sites Direct on-site measurement of fibre release during representative activities Employees need full PPE Samples collected using standard occupational hygiene methods Analysed by electron microscopy Fibres counted and identified Photos: 11

12 Is ABS a gold standard? Measures actual airborne fibre concentrations under reasonable worst case conditions Only possible at an existing property or postdevelopment Applicability under planning? But is it compatible with CAR2012? SoBRA protocol available for use under Part2A Uses fully enclosed outdoor raking of soil Estimate fibre release in the lab? The uncertainty in the relationship between soil and airborne concentrations has led to interest in novel fibre release potential tests More useful data for risk assessment than asbestos in soil concentrations Usually involve: Mechanical disturbance of dry soil/made ground samples Airborne fibres collected on filter Asbestos fibres counted (and identified) often expressed relative to dust concentrations (ie f/ml per mg m 3 dust) USEPA Fluidised bed asbestos segragator UK HSL dustiness test 12

13 Conclusions We understand the risks much better than the potential exposures Soils containing non-bound amphibole asbestos are of most concern How much is acceptable? UK policy? What about asbestos cement fragments? UK policy? Precautionary approaches = unnecessary remedial costs? Better knowledge of the Soil-air relationship is needed Ongoing work by JIWG/SOBRA: Background levels in soil Sobra fibre release protocols and database See JIWG area of the CLAIRE website Richard.ogden@lqm.co.uk Tel: Full contact details at : 13