1. Study of lung cancer due to airborne lead in the US
Lead is a heavy metal found in the air
Historically lead came motor vehicles. After phase out of leaded gasoline, a major source is now lead smelters
People are exposed to lead by breathing, and it accumulates in the blood
Health impacts are particularly a concern for children, and they include: damaged organs, nervous system, lower IQ, etc
Question: What is the health impact of airborne lead on lung cancer?
                                                                 

2. Some standards and statistics
National Standard for airborne lead
Quarterly average < 1.5 mg/m3
OSHA standard for blood lead
Concentration in blood < 25mg/100ml
National health statistics for lung cancer
1999 lung cancer incidence rate = 55 (per 100,000)
1999 lung cancer incidence = 150,000

3. Model-based health impact assessment
of lung cancer due to exposure to lead
Spatiotemporal monitoring
BME spatiotemporal mapping
f(PbA) E[PbA]
Exposure assessment, PbA(s,t)
Stochastic Toxicokinetics modelling
Log PbB=a+b log PbA
Dose assessment, PbB(s,t)
Epidemiological research /biostatistics
D= dt PbB(t)
SIR=1+(1/ h -1)(1-exp-3D/Ds)
H=(SIR-1)h
Health effect assessment, H(s,t)
Demographics, population p(s,t)
L=Hp
Population impact assessment, L(s,t)
Uncertainty evaluation

4. Exposure to airborne lead in the US
BME median estimate of airborne lead concentration (mg/m3)

5. Toxicokinetic lead model
Log(PbB)= log PbA (Lai et al., JIAOEH, 1997)

6. Dose of lead in the blood
due to exposure to airborne lead
BME median estimate of blood lead concentration (mg/100ml)

7. Dose of lead in the blood
due to exposure to airborne lead
BME 16% quantile of blood lead concentration (mg/100ml)
We expect people had at least this amount in the blood with only a 16% chance of being wrong

8. Epidemiology study for lung cancer
Cumulative lead dose in relation to Standardized Incidence Rate (SIR) of lung cancer (Lundstrom et al., SJWEH, 1997)

9. Dose / Health response model
Proposed model of health effect:
D= dt PbB(t)
SIR=1+(1/ h -1)(1-exp-3D/Ds)
H=(SIR-1)h
D = cumulated dose
= expected lung cancer incidence rate
Ds = saturation (lethal) dose

10. Lung cancer incidence rate
due to exposure to airborne lead
BME median estimate of lung cancer incidence rate (per 100,000) due to exposure to airborne lead from 1984 till year t)

11. Lung cancer incidence density
due to exposure to airborne lead
BME median estimate of lung cancer incidence density (per sqmi) due to exposure to airborne lead from 1984 till year t)

12. Exposure to airborne lead in the US

13. Dose of lead in the blood
due to exposure to airborne lead

14. Lung cancer incidence rate
due to exposure to airborne lead

15. Total incidence of lung cancer
due to exposure to airborne lead

16. Toxicokinetic sensitivity analysis
Lead model 2: Log(PbB)=a’+0. 6 log PbA

17. Toxicokinetic sensitivity analysis
Total incidence of lung cancer due to exposure to airborne lead using toxicokinetic models 1 and 2

18. Conclusion for airborne lead study
Model-based exposure mapping and health impact assessment provides a framework to assess the impact of airborne lead pollution on lung cancer in the US
The framework allows for an uncertainty evaluation
The analysis estimates a total incidence of 32,500+/-2,000 cases of lung cancer due to exposure from 1984 to 2000.
A sensitivity analysis shows that extrapolation of toxicokinetic models to low dose is a critical
Future work should consider stochastic toxicokinetic modelling