Risk Assessment of Lead for Japanese Infants and Children Based on Bloodlead Concentrations

1
Risk Assessment of Lead for Japanese Infants and
ChildrenBased on Blood-lead Concentrations

• Norihiro Kobayashi, Kikuo Yoshida
• Research center for Chemical Risk Management
  (CRM), National Institute of Advanced Industrial
  Science and Technology (AIST), Japan

2
Background

• Research Center for Chemical Risk Management has
  developed and released a number of risk
  assessment documents on the chemical substances
  with known or expected risks to human health
  and/or ecosystem in Japan. Lead is one of the
  target chemicals.
• Lead has been used in many consumer products,
  such as batteries, solders, water pipes, and so
  on. However, adverse effects for human health and
  ecosystem, particularly effect to infants nerve
  systems are concerned.
• Quantitative risk assessment of lead has not been
  conducted in Japan.

3
Procedure of Risk Assessment of Lead

• Estimation of Source and Emission
• Estimation of Environmental Fate
• Exposure Analysis
• Toxicity Analysis
• Human Health Risk Characterization
• Ecological Risk Characterization

4
Outline of Human Health Risk Characterization

• Target Population 0-6 years old children
• Endpoint Adverse effects to childrens center
  nerve system
• Critical level Blood lead concentrations of 10
  ug/dL
• Method to estimate blood-lead concentrations
• Application of IEUBK model (Integrated Exposure
  Uptake Biokinetic model for Lead in Children),
  which was developed by U.S. EPA (1994)
• Biomonitoring

5
Application of IEUBK model

• Input
• Environmental lead concentration (lead in air,
  soil/dust, food, water)
• Exposure factors ( amount of intake, uptake
  ratio, etc.)
• Output
• Distribution of blood lead concentrations
• Probability of blood lead concentration exceeding
  critical level

Soil
Dust
Water
Air
Food
ExposureCompartment
Lungs
Gastrointestinal Tract
Lungs
Feces
Gastrointestinal Tract
Uptake Compartment
Exhaled Air
Plasma Extra-Cellular Fluid
Feces
Plasma Extra-Cellular Fluid
RedBloodCells
OtherSoft Tissues
TrabecularBone
CorticalBone
Kidney
Liver
Biokinetic Compartment
Skin, Hair, Nails
Urine
Environmental Media
Body Compartment
Source U.S.EPA (1994)
Elimination pools of the Body
6
Environmental Lead Concentrations
Air-lead concentrations ng/m3
160

• Air
• Dramatic decrease in air lead concentrations is
  shown from 1970s to the present.
• Monitoring data of recent 5 years were used as
  the input.
• Soil
• Soil lead concentrations in Japan were
  investigated at 193 locations in 1999 by the
  Japanese ministry of environment.
• Geometric mean and geometric standard deviation
  of all monitoring data are 13.2 ug/g and 2.2,
  respectively.

140
120
100
80
ng/m3
60
40
20
0
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
Fiscal Year
Soil-lead concentrations ug/g
120
100
80
ug/g
60
40
20
0
Tokyo
Osaka
Miyagi
Niigata
Nagoya
Fukuoka
Hokkaido
Kawasaki
Hiroshima
Yokohama
All locations
Location
Source Japanese Ministry of Environment (2000)
7
Lead Intake from Food

• Instead of the lead concentration in food,
  results of the total diet study were used as the
  input.
• Lead intake from food is decreasing from 1970s
  to the present.
• Monitoring data of recent 5 years were used as
  the input.

Lead intake from food ug/kg/day
100
80
60
Lead intake ug/kg/day
40
20
Source National Institute of Health Science,
Japan (1977-2004)
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
Fiscal year
8
Lead Concentrations in Water

• Significant difference between the lead
  concentrations in first-draw water and flushed
  water were observed.
• These two types of monitoring data were used as
  the input.

Lead concentrations in water mg/L
0.1
First-draw water
Flushed water
0.01
Lead concentrations mg/L
0.001
Source Bureau of Water Works, Tokyo Metropolitan
Government, Japan (2001)
0.0001
ApartmentHouses
Detached Houses
9
Exposure Scenarios

• General populationExposed to average lead
  concentrations
• High exposure population
• High air-lead concentrations Exposed to
  maximum lead concentrations in air. (Increase of
  soil/dust lead concentrations corresponding to
  air concentrations were considered.)
• High soil-lead concentrations Exposed to
  maximum soil lead concentrations. (Increase of
  dust lead concentrations corresponding to soil
  concentrations were considered.)
• High water-lead concentrations Exposed to
  maximum lead concentration in tap water.

10
Results for General Population

• Probabilities of exceeding 10 ug/dL were less
  than 0.1 for all age.
• It is concluded that no risk reduction measures
  are required for the general population in Japan.

11
Results for High-Exposure Population

• For the children who are exposed to high-level
  water lead concentrations, risk levels were
  estimated to be close to 1.
• It may be considered that for the children who
  live in a house in which lead water pipes are
  used, it is better to reduce lead intake from
  water.

12
Contribution of Sources
Air
Soil/Dust
1
Air
Water
6
8
Soil/Dust
10
11
Water
9
Food
Food
83
72
High air-lead conc.
General population
Air
Air
Soil/Dust
1
1
3
Soil/Dust
21
Water
Water
8
Food
Food
45
52
70
High water-leadconc.
High soil-lead conc.
13
Risk Assessment Using Biomonitoring

• Outline
• Blood lead concentrations of 290 children who
  live in Shizuoka prefecture in Japan were
  measured.
• Research Period
• July, 2004 September, 2005

100
GM1.4 ug/dLGSD1.6
90
80
70
Log normal curve
60
50
Frequency
40
Distribution of blood leadconcentrationsfrom
biomonitoring
30
20
10
0
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
Blood lead concentrations ug.dL
14
Results of Biomonitoring

• For all age, blood lead concentrations and
  probabilities of exceeding 10 ug/dL were lower
  than the those of model estimation.

15
Summary

• Judging from the results of the model calculation
  and biomonitoring, it is concluded that urgent
  risk reduction measures for lead are not required
  at the current risk level in Japan.
• However, for children who are exposed to high
  level water-lead concentrations, risk levels were
  considered to be relatively high.
• For the population, lead intake can be easily
  reduced by not drinking first-draw water.

16
Announcement

• The results of this study was released as the
  risk assessment document on Sep.15 (in Japanese).
  
• This risk assessment document, is expected to be
  the scientific bases for the decision-making in
  risk management of lead among regulators,
  industries and public.