Chemical exposure via inhalation of soil derived dust - Road Rail by dfsiopmhy6

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									Chemical exposure via inhalation of
soil derived dust
Modelling versus measurement
                                           Outline

• The problem
• Assessing exposure via dust inhalation
  – Modelling
  – Measurement

• Conclusions



                                               2
                                                          The problem
• Dust inhalation is one of the modelled pathways in CLEA
• Exposure via dust inhalation is generally small relative to
  ingestion of soil + household dust
   – e.g. CLEA residential land-use, ADEdust = 0.3% ADEingest
• As a result, dust inhalation is only important when:
   – Inhalation toxicity >> oral toxicity; or
   – Dust inhalation is the only active pathway




                                                                  3
                                                             Problem contaminants
Dust                    HCVoral      HCVinhal       Ratio    Assessment Criteria     SGV or      Basis
important?
                       ug.kg-1.d-1   ug.kg-1.d-1   (inhal/           mg.kg-1          GAC
                                                     oral)    Oral         Inhal     mg.kg-1

     Arsenic             0.3          0.002        150        32              85      32        Oral
     Cadmium            0.36         0.0014        257        11              185     10      Integrated

     2-Chloro
                          80           0.286        280       1300             22      22      Integrated
      naphthalene
     Benzo[a]pyrene     0.02        0.00007        286        1.5             2.9     1       Integrated
     Copper              160          0.286        559       2660        10400      2330      Integrated
     Chromium (III)      150           0.1        1500      19500        3550       3000      Integrated
     Nickel              12           0.006       2000        531         127        130        Inhal
     Chromium (VI)        1          0.0001       10000      12.4             4.3    4.3        Inhal
     Asbestos             ?             ??        >1000?


                                                                                                    4
                            How do we assess dust exposure?
 • Most dust > PM10 caught in trachea
   + ingested
 • Particles in PM10 or PM2.5 range are
   able to reach lungs
                                             10–150 um
 • Smaller particles penetrate further,
   have longer residence times +
   therefore present greater risk
                                             1–10 um
                                  Conc. of
Exposure = Respiration
                       x [PM10] x contaminant <1 um
           rate
                                  on PM10


                     Measure or Model                    5
Modelling
                                                             CLEA model
• Different equations for exposure (mg.d-1) for outdoor +
  indoor inhalation:

                      1   Tout 
        IRout   = Cs      Vinh  
                      PEF   24 
                                    PM10 outdoors arising from soil
                                    (0.425 ug.m-3, residential)

                 1                   Tin 
        IRin = Cs     + Cs .TF .DL Vinh  
                 PEF                 24 
            Contaminant concentration           PM10 indoors
            in PM10 indoors                     (50 ug.m-3, residential)   7
                                     Inhalation of dust outdoors
• 1/PEF (i.e. PM10 from soils) calculated using Cowherd’s
  model + air dispersion model        1       J
                                                  =        w
                                          PEF         Q
                                                          Cwind
• Jw = PM10 emission flux (g.m-2.s-1) estimated using Cowherd
                              3
                       u                (1-V) = fraction of site with bare soil
        J w = (1 − V ).
                       u     .F ( x )
                             
                                          u = average windspeed at 10m height
                                          ut = threshold windspeed at 10m height
                        t               F(x) = empirical factor based on u:ut

• Jw = 1 x 10-6 g.m-2.s-1 for residential land-use
                                                                              8
                                                 Inhalation of dust outdoors
• Q/C = dispersion factor estimated using US EPA AERMOD PRIME
• PM10 increases with
                                                 4000
                                                                                          Belfast
                                                 3500

  increasing area
                                                                                          London
                                                 3000                                     Newcastle
                                                                                          Plymouth

• Are predicted PM10 concs
                                                 2500




                                       Q/Cwind
                                                 2000

  realistic?                                     1500


    Predicted PM10 for > 1 ha                   1000

                                                 500
     bare earth site ≈ 40 ug.m-3
                                                   0

• Are predicted contam concs                            0.01   0.1

                                                                     Site area (ha)
                                                                                      1               10




  in air realistic?
    Predicted air conc of As using this PM10 & 20mg.kg-1 in soil = 0.8 ng.m-3
    UK average air conc As for rural areas = 1 to 4 ng.m-3
• But note: uncertainties in Cowherd model are HUGE!
                                                                                                       9
                                           Inhalation of dust indoors
• What is indoor dust composed of?
  – Many things, e.g. soil particles, hair, skin,
    fibres, pollen, dust mites, soot, ash, animal
    fur and dander, food, building components
  – PM10 < 10% by mass of typical house dust
    collected in hoover bag?
  – Composition is highly variable between
    houses

• Contaminants in house dust
  – Tracked back soil/dirt
  – Outdoor air
  – Internal sources

                                                                 10
                         Estimation of exposure – indoor dust
                                                    inhalation
• Indoor air PM10 = dust loading factor (DL)
   – Range of values reported by Oomen + Litzen, 2004 = 12.6 to 157 ug.m-3
   – Highest value occurred for a school
   – WHO (1989) give range of 20 to 60 ug.m-3
   – CLEA assumes 50 ug.m-3 for UK houses – is this reasonable?

• Concentration of contamination in PM10 = Cs x TF
   – TF = transport factor and should be contaminant specific
   – Default value = 0.5, i.e. concentration of contaminant in PM10 = half the
     concentration in soil




                                                                                 11
                                                                                                          Transport factor
                                                                                      1

• Trowbridge & Burmaster (1997)                                                      0.9
                                                                                     0.8
       – found reasonable correlation between                                        0.7
                                                                                     0.6
         conservative tracer components in                                           0.5




                                                                                TF
         garden soil + indoor dust                                                   0.4
                                                                                     0.3
       – Mean TF = 0.43                                                              0.2
                                                                                     0.1
• But, TF varies for many                                                             0
                                                                                           Al   Ce   Fe   Hf    K   La   Mn   Na      Sc   Sm   Th        V
  contaminants and can exceed 1 due
  to enrichment                                                                                                Rasmussen et al, 2001


       – E.g. Cu, Cd, Pb, Zn (Culbard et al, 1988,                                              Pb in
                                                                                                dust
         Rasmussen et al, 2001, Oomen +Litzen,                                                  mg.kg-1
         2004)
       – Pb can be up to 3?
       – PAHs?                                                                                                           Pb in soil
Trowbridge PR, Burmaster DE 1997. A parametric distribution for the fraction of outdoor soil in                          mg.kg-1
                                                                                                                                                     12
indoor dust. J Soil Contam 6: 161–168
Measurement
                                                                       Research
• Preliminary research on dust exposure in UK:
   – Amateur research on my house in 2009
      • Comparison of PAH concentrations in house dust + garden soil
      • Measuring PM10 indoors
   – Current research by Dr Chris Collins, University of Reading
      • Comparison of PAH concentrations in house dust + garden/allotment soils
      • Measuring PM10 indoors
      • Measuring PAH concentrations in suspended dust




                                                                                  14
                                                   Measuring PM10
• Air pump with filter sent to lab for gravimetric analysis ( ≈ £10/sample)
• Infrared refractive sampling e.g. Casella DustPro monitor ( ≈ £2500)
• Laser photometry e.g. Turnkey Instruments Osiris ( ≈ £6000)
• Real-time gravimetric analysis e.g. Thermo Partisol 2025 ( ≈ £16000)




                                                                         15
                                            Chemical analysis of suspended dust
  • University of Reading using passive sampling technique developed by
    Abdallah & Harrad (2010)
         – Polyurethanefoam disk for assessing vapour phase PAHs
         – Glass fibre filter for assessing particulate sorbed PAHs




Abdallah, MAE & Harrad, S. 2010. Modification and Calibration of a Passive Air Sampler for Monitoring Vapor and Particulate
                                                                                                                              16
Phase Brominated Flame Retardants in Indoor Air: Application to Car Interiors. Environ. Sci. Technol. Vol. 44, 3059–3065
PM10 indoors – my house – DustPro results
                 0.1

                                                                                   10 sec average
                0.09
                                                                                   5 min average
                                              Hoovered
                0.08
                                              for 10
                                              mins
                0.07

                0.06
 PM10 (mg/m3)




                0.05

                0.04

                0.03

                0.02
                                                    • PM10 indoors measured using
                0.01
                                                      Casella DustPro= 30 to 40 ug/m3
                  0
                   06:43   06:57   07:12   07:26   07:40   07:55   08:09   08:24   08:38   08:52    09:07
                                                                                                            17
                                                               PM10 indoors – my house – Osiris results
                             180
                                                                                                                                                                                     •   PM10 = 8 to 97
                                                                                                                                                              total
                             160                                                                                                                                                         ug.m-3
                                                                                                                                     Leave                    PM10
                                                                                                                                     for                      PM2.5
                                                                                                                                                                                     •   PM2.5 = 4 to 24
                             140                                                             Get up                                  school
                                                                   Gone to bed                                                                                PM1                        ug.m-3
Dust concentration (ug/m3)




                             120
                                                                                                                                                                                     •   Average PM10 =
                                                                                                                                                                         Wife +
                             100                                                                                                         Wife +                          kids gets       15 ug.m-3
                                                                                                                                         youngest                        back
                                                                                                                                         leave
                                                                                                                                                                                     •   Average PM2.5
                              80
                                                                                                                                                                                         = 6 ug.m-3
                              60

                              40

                              20

                               0
                                   22:00

                                           23:00

                                                   00:00

                                                           01:00

                                                                     02:00

                                                                             03:00

                                                                                     04:00

                                                                                             05:00

                                                                                                     06:00

                                                                                                             07:00

                                                                                                                     08:00

                                                                                                                             09:00

                                                                                                                                      10:00

                                                                                                                                              11:00

                                                                                                                                                      12:00

                                                                                                                                                                 13:00

                                                                                                                                                                          14:00
                                                                                                                                                                                                   18
                       Soil to dust transport factor – my house
• What proportion of PM10 is likely to be from garden soil?
• 2 lines of evidence:
   – PAH analysis of dust from hoover bag vs soil analysis
      • Average [BaP] in surface soil = 1.2                                   20%

        mg/kg                                                                 18%
                                                                                                                                                 Naphthalene
      • [BaP] in dust = 1.0 mg/kg                                             16%                                                                Acenaphthylene
                                                                                                                                                 Acenaphthene




                                                % contribution to total PAH
      • PAH profile in dust similar to garden                                 14%                                                                Fluorene
                                                                                                                                                 Phenanthrene
        soil                                                                  12%                                                                Anthracene
                                                                                                                                                 Fluoranthene

  – SOM analysis of dust from hoover                                          10%                                                                Pyrene
                                                                                                                                                 Benz(a)anthracene
                                                                              8%
    bag vs soil analysis                                                                                                                         Chrysene
                                                                                                                                                 Benzo(b)fluoranthene
                                                                              6%                                                                 Benzo(k)fluoranthene
      • Average SOM in surface soil = 13%                                                                                                        Benzo(a)pyrene
                                                                              4%                                                                 Indeno(123cd)pyrene
      • SOM in dust = 32%                                                                                                                        Dibenzo(ah)anthracene
                                                                              2%                                                                 Benzo(ghi)perylene
      • If we assume that dust composed of
                                                                              0%
        soil (13% SOM) + skin/food (100%                                            DS-1 HA1-1 HA1-2 HA1-3 HA2-1 HA3-1 HA4-1 HA5-1 HA6-1 HA7-1
        SOM), TF = 0.8 – higher than CLEA
        generic assumption!
                                                                                                                                                    19
University of Reading study
      • Sampled and analysed
        soils from garden +
        allotment (0.5 miles
        from house) for PAHs
      • Sampled and analysed
        house dust from hoover
        bag for PAHs
      • Indoor air PM10
        monitoring using Osiris
      • Passive suspended dust
        sampling for PAHs

                              20
                                                   University of Reading results
                                1.60                        • Very similar PAH profiles
                                1.40
                                       Allotment              between garden soil,
                                                              allotments soil + house
                                       Garden
                                1.20   Dust

                                                              dust
Concentration relative to BaP




                                1.00


                                0.80
                                                            • Awaiting PM10 + passive
                                                              sampler results
                                0.60


                                0.40


                                0.20


                                0.00




                                                                                   21
                                                                    Conclusions
• Dust inhalation indoors is a key pathway for BaP, Ni, Cr(VI) and
  asbestos
• Key uncertainties:
   – PM10 – Highly variable – need long-term monitoring in occupied buildings to
     determine
   – Transport factor - Varies significantly from site to site + contaminant to
     contaminant
• Hoover bag analysis helps check on TF but may not be valid for
  respirable particles
• Further research required to ascertain if there is a correlation between
  concentrations in soil + respirable dust (especially for PAHs + asbestos)
• Why is HCVinhal << HCVoral for BaP, Ni + Cr(VI)?
                                                                                   22

								
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