RECOMMENDATION FOR AIR MONITORING DURING ENVIRONMENTAL INVESTIGATIONS OF CHILDHOOD LEAD POISONINGS

Transcription

1 RECOMMENDATION FOR AIR MONITORING DURING ENVIRONMENTAL INVESTIGATIONS OF CHILDHOOD LEAD POISONINGS by Wilbert L. Townsend, CIH/MPH/MBA Chronic Disease Epidemiologist Southern Nevada Health District Las Vegas, Nevada Phone: (702)

2 OBJECTIVES Understand the relevance of monitoring for airborne lead during investigations of childhood elevated blood lead levels Define a method and identify equipment for monitoring airborne lead concentration Identify and apply an air lead and blood lead model

3 INTRODUCTION Importance of lead source identification Typical residential investigations of childhood lead poisonings (NO AIR MONITORING) The airborne versus ingestion contribution to childhood lead exposure Inhalation contribution is small but significant?

4 PURPOSES To explore the concentration of airborne lead necessary to elicit an elevated blood-lead level (BLL) in a child between the ages of 0 and 6 years and to monitor the residential (indoor) environment to see if such a level was reached To monitor the indoor air to see if the airborne concentration was sufficient to raise a child s BLL to the level of the United States Centers for Disease Control and Prevention (CDC) standard of ten micrograms per deciliter of whole blood (10 µg/dl)

5 REGULATORY GUIDANCE AND STANDARDS Blood CDC (Child) = 10 µg/dl; [CDC Guidance 1997] OSHA (Adult) = 40 µg/dl; [29CFR (j)(2)(i)(B)] CDC (Adult) = 25 µg/dl; [DHHS (NIOSH ALERT) Publication No a] Air OSHA (Adult) = 50 µg/m 3 per 8-hours; [29CFR (c)(1)] EPA (Child & Adult) = µg/m 3 per 24-hours (1.5 µg/m 3 per Calendar quarter); [40CFR50.12]

6 CHILD PHYSIOLOGICAL DATA 0 TO 6 YEARS OLD Inhaled Air in 24-hour period = 5 to 6 m 3 Blood Volume 2 L Lead Absorption Rate = 5 X Adult s Blood Lead Level = > 90% Respiratory Tract Deposition

7 LEAD EXPOSURE PATHWAYS IN CHILDREN Ingestion Inhalation In utero Skin absorption

8 LEAD TOXICITY IN CHILDREN Affects all bodily systems CNS - Irreversible Neurobehavioral Deficits - Learning Impediment - Lowering of IQ A-2 Carcinogen (IARC, Group 2A, Feb 04)

9 MATHEMATICAL MODEL ln(bll) = 0.24*ln(Air Lead Level) ; [Hayes, EB, et.al., Pediatrics 93: , 1994] ln(bll) = *(Air Lead Level) ; [Rothenberg, SJ., et.al, EH Perspectives 112(10): , 2004] ln(bll) = 0.24*ln(Air Lead Level) ; [Lai, JS, et.al., Int Arch Occup Environ Health 69: , 1997] Hayes model (most conservative project focus)

10 Blood Lead Level vs. Air Lead Level(Logarithmic Scale) 20 Blood Lead Level(mcg/dL) Air Lead Level(mcg/m3)---Logarithmic Scale Hayes et.al. Rothenberg et.al. Lai et.al.

11 Determination of Minimum Airborne Lead Concentration Using Hayes, et.al., model - Long-term effects on children < 6 years - Critical BLL = 10 µg/dl - Substitution: Solve for Air Lead Level ln(10) = 0.24*ln(Air Lead Level) ln(air Lead Level) = [ln(10) ]/0.24 Critical Air Lead Level = µg/m 3

12 Lead Particles Tracked into Homes May Become Airborne Various Sizes and Settling Rates Suspended Indefinitely (if aerodynamic diameter < 1 µ) Lung - Blood Absorption (> 90% indefinitely suspended particles)

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14 Lead Loading of Floor Coverings and Survey Instrumentation Lead Loading (µg/ft 2 or µg/cm 2 ) is a measure of the degree of contamination Survey Instrument LOD = 100 µg/cm 2 Theoretical Average Lead Loading for critical airborne lead level may be beyond survey instrument LOD (see later)

15 Typical Environmental Investigations of Homes of Children with Elevated BLLs Questionnaire Building material, Soil, Water, Foods Furniture, Cookware, Toys, etc. Did not identify a positive source of lead exposure (NO AIR MONITORING)

16 MATERIALS AND METHOD Preliminary Activities Calculation of Minimum Lead Contamination of Floor Covering to Yield a Critical BLL in Children Ages 6 Years and Younger Calculation of Sampling Time Necessary to Collect Sufficient Sample for Analysis Selection of Statistically Valid Sample of Residences (95% CI) Administration of Telephone Questionnaire

17 Table 1: Minimum Lead Contamination of Floor Covering to Yield a Critical BLL in Children Ages 0 to 6 Room Volume (ft 3 ) = 15*20* Room Volume (m 3 ) Floor Area (ft 2 ) Critical Air Concentration 2 (µg/m 3 ) Lead in Room (µg) Floor Lead Loading (µg/ft 2 ) or {µg/cm 2 } = 3000/35.31 = 15*20 = e (ln(10) 3.17)/0.24 = 85*0.027 = 2.29/ {8.61E-6}

18 Table 2: Calculation of Sampling Time to Collect Sufficient Sample Volumetric Flow Rate (m 3 /min) Critical Air Concentration 2 (µg/m 3 ) Mass Flow Rate (µg/min) Method LOD (µg/m 3 ) Method LOD (µg) = 9/1000 = e (ln(10) 3.17)/0.24 = 0.009*0.027 = 0.01 = 0.009*1440* Sampling Time (hrs) =0.1296/(60* ) 8.9

19 MATERIALS AND METHOD Investigative Activities Target Residences - LP or EBLL Children - Pre-1979 Conduct Comprehensive Environmental Investigation Including Air Monitoring

20 INDOOR AIR MONITORING Accomplished using calibrated air-sampling pumps configured appropriately with multi-stage cascade impactors and pre-loaded PTFE filters Impactors assembled with 25mm and 37mm PTFE filters collected particles having aerodynamic diameters less than 1 micron Pre-loaded 37mm PTFE filters (closed face) were used to collect total dust Volumetric Flow Rate (9.0 L/min)

21 AIR SAMPLING ASSEMBLY

22 ENVIRONMENTAL SURVEY Onsite Detection of Lead in Materials - Paint - Floor and Wall Tiles - Cookware and Pottery - Toys Accomplished Using X-ray Fluorescence Device

23 Portable X-ray Fluorescence Device in Use

24 AIR SAMPLE ANALYSIS AIHA-Accredited Laboratory Graphite Furnace Atomic Absorption Spectroscopy LOD was µg/m 3

25 RESULTS Relationship Between Airborne Lead Levels and Corresponding Children BLLs Prediction of Children BLLs From Air Lead Levels Using Hayes et.al., Model Comparison of Predicted BLL Results and Actual BLL Results

26 Figure 2. Relationship Between Airborne Lead Levels and Corresponding Children BLLs Blood Lead Conc ( mcg /d L ) 10 y = x R 2 = Air Lead Conc (mcg/m3)

27 Figure 3. Prediction of Children BLLs From Air Lead Levels Using Hayes et.al., Model Blood Lead Conc (mcg/dl y = Ln(x) R 2 = Air Lead Conc (mcg/m3)

28 Figure 4. Comparison of Predicted BLL Results and Actual BLL Results Predicted BLL (mcg/dl y = x R 2 = p = Actual BLL (mcg/dl)

29 CONCLUSION Lead exposure still remains a preventable childhood issue in our society Pre-1979 residences pose a significant threat from airborne lead exposure to children health in Clark County, NV Indoor air monitoring for lead can play a vital role in determining the source of EBLLs in children Indoor air monitoring for lead should be part of the standard protocol in evaluating children with EBLLs, particularly those living in pre-1979 residences

30 THANK YOU FOR YOUR ATTENTION!