 



Tracking blood lead levels 

The Centers for Disease Control and Prevention (CDC) tracks children’s
blood lead levels (BLLs) in the United States using three methods: (1)
nationally representative surveys (2) state and local surveillance and
(3) local prevalence surveys.  Because lead exposure in children varies
among populations and communities, all three approaches are needed to
understand the burden of elevated BLLs among young children across the
United States. 

 

Defining the problem 

Together, the three data sources enable CDC to describe children at risk
and to measure trends in BLLs among young children.  Special attention
is given to BLLs ((10 micrograms per deciliter ((g/dL).  Many studies
point to a link between BLLs ((10 (g/dL and harmful health effects, in
particular learning disabilities and behavior problems. The Department
of Health and Human Services’ Healthy People 2010 initiative has set a
national goal of eliminating BLLs ((10 (g/dL among children aged 1-5
years by 2010.  CDC also tracks BLLs in adults using NHANES and state
surveillance (  HYPERLINK "http://www.cdc.gov/niosh/ables.html" \t
"_self"  ABLES ) 

 

National surveys 

The National Health and Nutrition Examination Surveys (NHANES),
conducted by CDC's National Center for Health Statistics, have been
tracking BLLs in the United States since the 1970s (NHANES). These
national surveys are designed to estimate BLLs at the national level
only not at the state or local levels. NHANES have documented a
substantial decrease in BLLs among young children. The NHANES II
1976-1980 reported a geometric mean BLL of 15 µg/dL among children aged
1-5 years. The most current NHANES (1999-2000) data show that geometric
mean BLLs continue to decrease in young children.   

BLLs >=10 µg/dL were estimated for 2.2% of children aged 1-5 years
according to NHANES 1999-2000. The 2.2% estimate translates to 434,000
children with a 95% confidence interval from 189,000 to 846,000
children. This confidence interval means that there is a 95% probability
that the true number is within that range. Future NHANES should help
confirm the trends shown in Table 1. 

Table 1.  NHANES Blood Lead Level Measurements for Children Aged 1-5
Years by Year of NHANES, United States 

 

Year

Geometric Mean1 BLLs  (95% CI2)

Prevalence3 of BLLs >=10 µg/dL4

(95% CI)

Estimated Number of Children with BLLs >=10µg/dL 

(95% CI)

1976 - 1980

14.9

(14.1 - 15.8)

88.2%

(83.8 - 92.6)

13,500,000

(12,800,000 - 14,100,000)

1988 - 1991

3.6 

(3.3-4.0)

8.6%5 

(4.8-12.4%)

1,700,000 

(960,000-2,477,000)

1991 - 1994

2.7 

(2.5-3.0)

4.4% 

(2.9-6.6%)

890,000

(590,000-1,330,000)

1999 - 2000

2.2

(2.0-2.5)

2.2%

(1.0-4.3%)

434,0006 

(189,000-846,000)



 

1  A measure of central tendency that differs from an arithmetic mean
because it uses multiplication rather than addition to summarize the
data values   

2 This confidence interval (CI) means that there is a 95% probability
that the true number is within that range   

3 The number of children with BLLs >=10 (g/dL over the whole population
at a given point in time   

4 CDC has determined a blood lead level (BLL) 10 micrograms per
deciliter ((g/dL) to be a level of concern   

5 This estimate differs slightly from values published previously due to
updates in coding and weighting of the survey data.   

6 This estimate differs slightly from values published previously due to
weighting of the survey data. 

 

  HYPERLINK "http://www.cdc.gov/nceh/lead/research/kidsBLL.htm" \l
"top#top"  Back to top 

  

State and local surveillance 

To obtain state and local estimates, CDC supports state and local child
blood lead surveillance systems.  Many states target their screening
resources to children considered at highest risk.  This approach makes
good use of limited funds but does not necessarily produce data
representative of all children aged 1-5 years.  Therefore, estimates
obtained from state and local surveillance data  cannot be directly
compared to   HYPERLINK "http://www.cdc.gov/nchs/nhanes.htm" \t "_self" 
NHANES . 

State surveillance data show that the risk for BLLs ((10 (g/dL in
children tested remains high in some counties and varies greatly among
states. Analysis of data from 19 states that received all BLLs of
children from laboratories for calendar years 1996 through 1998 have
shown that the proportion of children with BLLs ((10 (g/dL among those
tested for lead by state ranged from 2.7% to 14.9%.  Within individual
states the proportion of children with BLLs ((10 (g/dL, among those
tested, varied considerably.  For example, in Ohio, the range of the
proportion of BLLs ((10 (g/dL among children tested ranged from 1.3% in
one county to 27.3% in another.  Across all 19 states, the
county-specific proportions of children with BLLs ((10 (g/dL ranged from
0.5% to 27.3%. (  HYPERLINK
"http://www.cdc.gov/mmwr/preview/mmwrhtml/mm4950a3.htm" \t "_self"  MMWR
2000 ).

 

Prevalence surveys 

CDC supports local prevalence studies that are representative of the
area studied.  A study in Chicago found that in one community, more than
20% of the children aged 1-5 years had BLLs ((10 (g/dL. Other state and
local health departments are making plans to conduct similar studies to
assess the extent of the problem in high risk communities. 

Prevalence studies provide the best local estimates of children with
BLLs ((10 (g/dL; however, these studies involve the time and effort of
many people.   For this reason, prevalence studies may be useful in
areas suspected to have a large number of families at high risk for BLLs
((10 (g/dL, such as those families who have low incomes, who live in
pre-1950 deteriorated housing, and who are minorities.

 

Next steps 

Specifically, CDC will place more emphasis on state and local
surveillance to understand the burden of BLLs ((10 (g/dL among young
children.  CDC will increase efforts to improve the quality of state and
local surveillance data and to share findings.  A report on state
surveillance data is planned for summer 2003. 



