The association between urban soil lead contamination and children's blood lead poisoning

Association Between Soil Lead and Blood Lead - Evidence

Mark Laidlaw, PhD


Link to my publications


New York Times Article - 1925

In 1925, The New York Times Published the following words of Dr. Yandell Henderson, Professor of Applied Physiology at Yale University: “…the breathing day by day of fine lead dust from automobiles using leaded gasoline will produce chronic lead poisoning on a large scale in the population of cities…” and would cause “… vast number of the population to suffer from slow lead poisoning…”. He stated that “…This is probably the greatest single question in the field of public health that has ever faced the American public…”. Furthermore, he stated that “…It is the question whether scientific experts are to be consulted, and the action of the Government guided by their advice; or whether, on the contrary, commercial interests are to be allowed to subordinate every other consideration to that of profit".

To read the entire story, see the original article in the New York Times (1925)

Caltech Professor Clair Patterson stated the following in 1980: “Sometime in the near future it probably will be shown that the older urban areas of the United States have been rendered more or less uninhabitable by the millions of tons of poisonous industrial Pb residues that have accumulated in cities during the past century………Extrapolating from present information, …probably… it will be shown in the future that average American adults experience a variety of significant physiological and intellectual dysfunctions caused by long-term chronic lead insult to their bodies and minds which results from excess exposures to industrial lead that are five hundred-fold above natural levels of lead exposure, and that such dysfunctions on this massive scale may have significantly influenced the course of American history(NRC, 1980; see p. 265-349). This pivotal and controversial statement of Clair Patterson’s provided inspiration for this website.

Link to map of lead poisoning risk in every neighbourhood of America - Source Vox and Washington State (Note - interactive map may not work in Microsoft Explorer browser)

The three main sources of lead exposure in urban environments are:

1) Soil (from leaded gasoline, exterior lead paint and lead smelters);
2) House Dust (from lead in soil and interior paint particles);
3) Water (from lead water lines)

This website focuses mainly on soil lead and does not thoroughly discuss the lead paint and water sources.

The lead emitted from gasoline (see line in blue) in high traffic inner city areas between the 1920's and 1980's (in the US) was deposited and incorporated within the top 5-10 centimetres of the surrounding soils. We now know that the lead in these soils can become resuspended into the air where it migrates into homes. People and pets also track the lead contaminated soil into homes. Children and adults are then poisoned. This, and in certain cases exposure to flaking lead paint and lead from lead water pipes, has resulted in epidemics of lead poisoning in large parts of some inner-city areas. This is a global phenomenon and will continue until lead in soil dust in urban areas is isolated.

Source - Laidlaw and Filippelli (2008)

To read the REAL history of Lead in Gasoline, read The Ethyl Controversy by Professor William Kovarik.

Historical emissions of lead into the atmosphere from past use of lead in gasoline (petrol) between 1950 and 1982 in 90 urban areas of the United States (Mielke et al., 2011)

Source - Mielke, Laidlaw and Gonzales (2010)

An example of the lead poisoning epidemic - Detroit, Michigan

Note that the cases in this picture likely only represent a portion of the the total number of cases as typically blood lead is drawn from less than the full population.




The above map shows the number of lead poisoning incidences per address/home in the City of Detroit. The yellow dots show that there are 4,610 homes in the city with two occurrences per home; these are the most frequent. However, the blue dots, which show three to five or six to nine occurrences per home, cover more of the map because of the higher number of people affected. There was one home in the southwest portion of the city that had 17 lead poisoning cases, according to the map.


Early Childhood Lead Exposure and Academic Achievement:Evidence From Detroit Public Schools, 2008–2010 (Zhang et al, 2013)

A Strange Ignorance:The role of lead poisoning in failing schools(Michael T. Martin, Research Analyst, Arizona Public Schools)

Note the soil lead background concentrations in Detroit's northern suburbs.

View Lead Poisoning Percentages in Each Detroit School

Source - Detroit Free Press

Plot of Soil Lead Versus Children's Blood Lead in Detroit - Bickell 2010

This chart shows that when soil lead concentrations increase, children's blood lead levels increase.

Source - Bickell (2010)

Plot of Temporal Variation in Atmospheric Soil and Lead in Detroit - 2001-2009

This plot shows that soil that has been resuspended into the atmosphere is highly correlated with air lead concentrations. This is important as it indicates that air lead levels are linked with surficial soil lead concentrations. Therefore, reducing air lead concentrations must involve isolation of urban lead contaminated soils

Scatterplot with median splines of weather adjusted air lead and air soil in time (daily). Weather-adjusted air Pb and soil estimates (µg/m3) are graphed on the daily time-step, fitting distributions of air Pb and soil values with median splines.

Source - Zahran S., Laidlaw M.A.S., McElmurry S.P., Filippelli G.M. Taylor M. (2013)

Supplemental Material

Plot of Temporal Variation in Atmospheric Lead and Children's Blood Lead in Detroit - 2001-2009

This plot shows that children's blood lead levels are highly correlated with atmospheric lead concentrations (which are correlated with atmospheric soil on the previous page). This is important as it is apparent that to reduce children's blood lead levels, soil lead contamination must be isolated. Furthermore, this plot indicates that Pb paint is not thought to be attributable to seasonal variations in children's blood lead levels.

Weather-adjusted air Pb (µg/m3) and blood Pb (µg/dL) by age group. Average monthly child blood Pb levels adjusted by local weather conditions, child gender, method of blood draw, and census tract fixed effects

Source - Zahran S., Laidlaw M.A.S., McElmurry S.P., Filippelli G.M. Taylor M. (2013)

Supplemental Material

Source of Data- State of Michigan

In Flint, Michigan (USA), a public health crisis resulted from the switching of the water supply from treated Lake Huron water to untreated corrosive water sourced from the Flint River in April 2014, which caused lead to leach from water lines exposing a portion of the children in the city. The quarterly blood lead levels of children <6 years old in Flint (as well as in the State of Michigan and Genesee County) were compiled between 2010 and 2015 and the percentage of children with blood lead levels ≥5 µg/dL were calculated by the Michigan Department of Environmental Quality (MDEQ). The percentage of children with blood lead levels ≥5 µg/dL in the third quarter of 2013 (before the water source switch) rose from about 3.6% to about 7% in July–September) 2014 (see Figure 2 below). This figure clearly shows the seasonal nature of children’s blood lead pattern between 2010 and 2015 with a peak in the third quarter and a trough in the first or second quarter. The questions that are not being asked is why did children’s blood lead levels display a seasonal blood lead pattern before the introduction of the new water supply in Flint; and what are the implications of these seasonal blood lead patterns? Based on our interpretation of blood lead seasonality in urban areas such as Detroit (located approximately 100 km southeast of Flint), we infer that before the change in water supply the blood lead peaks in the third quarters in Flint were being driven by seasonal resuspension of lead dust from contaminated soils into the atmosphere during dry periods. This lead source may have been compounded by contributions from lead leaching from water pipes during the summer. This longer-term view of lead uptake via blood lead levels indicates that the blood lead peaks in the third quarters of 2014 and 2015 may have been driven by a combination of lead from resuspended soil-derived dust and lead newly released from water lines.


Average estimated soil lead concentration by census tract in Flint, Michigan.

Source - Laidlaw et al.(2016)

Children's Blood Lead Seasonality - State of Michigan: 1999-2012.

Source - Zahran et al.(2017)

In many urban inner-city areas of the United States, there is an epidemic of childhood blood lead poisoning (Gould, 2009). It has been estimated that 24.5%, or 9.6 million U.S. children have a blood lead in the range of 2 to 10 micrograms per decilitre, a level which will cause sub-clinical signs (Gould, 2009). The National Health and Nutrition Examination Survey (NHANES) III 1999-2002 database indicates that approximately 2.4 million children have blood Pb levels between 5 and 9.9 microgram/deciliter (Iqbal et al., 2008) and that within that population of 1-'5-year olds with blood Pb levels of 5 microgram/deciliter or higher, the prevalence was 47% for non-Hispanic Black children, 28% for Mexican American children, and 19% for non-Hispanic White children (Bernard and McGeehin, 2003). The fact that children of color are nearly 4 times more likely than white children to have blood Pb levels between 5 and 10 microgram/deciliter (and 13 times more likely to have blood Pb levels above 20 microgram/deciliter) (Bernard and McGeehin, 2003) raises concerns about social justice and the long-term health of these children. In addition, in 2004, in 10 ABLES states, a total of 10,527 females aged 16--44 years were tested, and all BLLs for this group were reported. Of the number tested, 1,370 (13.0%) had BLLs >5 µg/dL (10.9 per 100,000 female residents aged 16--44 years). I have not located the breakdown by race or by urban versus suburban area yet.

Childhood lead poisoning is a major environmental justice issue.

Leech et al. (2016) Article - Inequitable Chronic Lead Exposure:A Dual Legacy of Social and Environmental Injustice.

Why it is Important to Understand Exposure to Lead in Soil Dust

Childhood lead poisoning (Zahran et al., 2013a), (Zahran et al., 2013b) and preeclampsia/eclampsia (Zahran et al., 2014) have been shown to be associated with lead in soil and dust.

1) Childhood lead poisoning is one of the most common pediatric health problems in the United States today (CDC, 2014); Source
2) “Preeclampsia ... is the leading cause of maternal death worldwide and a major cause of preterm delivery”.... "Predicting preeclampsia is a major step towards saving the lives of many women”.Source
3) Lead is associated with autism: Dickerson et al.,2016.pdf;Kim et al. 2016;Mostafa et al. 2016;Gorini et al., 2014;Laidlaw and Mielke, 2015;Rossignol et al., 2014

Low PbB levels (<10 ug/dL) typically associated with urban soil Pb exposure are associated with a myriad of health outcomes. Low PbB levels (<10 ug/dL) are associated with Attention-Deficit Hyperactivity Disorder (ADHD)(Nigg et al., 2010), a reduction in children’s tests scores for reading (odds ratio = 0.51, p = 0.006) (Chandramouli et al., 2009), writing (odds ratio = 0.49, p = 0.003) (Chandramouli et al., 2009; Miranda et al., 2007) and mathematics (Miranda et al., 2007). Canfield et al. (2003) observed that when lifetime average PbB concentrations in children increased from 1 to 10 mg/dL, the intelligence quotient (IQ) declined by 7.4 points. Jusko et al. (2008) observed that compared with children who had lifetime average PbB concentrations < 5 mg/ dL, children with lifetime average concentrations between 5 and 9.9 mg/dL scored 4.9 points lower on Full-Scale IQ (91.3 vs. 86.4, p = 0.03). Similarly, Surkan et al. (2007) observed that children with 5-10 mg/dL had 5.0 (S.D. 2.3) points lower IQ scores compared to children with PbB levels of 1-2 mg/dL (p = 0.03). Interestingly, multiple studies have shown that that the strongest Pb effects on IQ occurred within the the first few micrograms of PbB (Schnaas et al., 2006; Canfield et al., 2003; Lanphear et al., 2005). Low PbB levels (<10 ug/dL) have also been associated with various physiological outcomes such as kidney damage (Fadrowski et al., 2010), dental caries (Moss et al., 1999), puberty delay in boys (Williams et al., 2010) and girls (Selevan et al., 2003) and cardiovascular outcomes in adults (Navas-Acien et al., 2007).

Link to United States National Toxicology Program Monograph on Health Effects of Low-level Lead (June 2012)

For a recent review of the health effects of lead exposure, see Bellinger, 2011. Another good article to read is titled Epigenetics of early-life lead exposure and effects on brain development by Senut et al. (2012).

Evidence of Health Effects Associated With Low Level Lead Exposure - National Toxicology Program

Link to United States National Toxicology Program Monograph on Health Effects of Low-level Lead (June 2012)
System affectedPopulationNTP ConclusionPrincipal Health EffectsBlood Lead (µg/dL)
NeurologicalAdultSufficientIncreased incidence of essential tremorYes, < 10
  LimitedPsychiatric effects, decreased hearing,Yes, < 10
   decreased cognitive function, increased 
   incidence of amyotrophic lateral sclerosis 
  LimitedIncreased incidence of essential tremorYes, < 5
 ChildrenSufficientDecreased academic achievement,Yes, < 5
   intelligence quotient, and specific cognitive 
   measures; increased incidence of attention- 
   related behaviours and problem behaviours 
  Sufficientdecreased hearingYes, < 10
 ChildrenLimitedIncreased hypersensitivity/allergy by skinYes, < 10
   prick test to allergens and increased 
   immunoglobulin* (not a health outcome) 
  InadequateAsthma, eczemaUnclear
CardiovascularAdultSufficientIncreased blood pressure and increased riskYes, < 10
   of hypertension 
  LimitedIncreased cardiovascular-related mortalityYes, < 10
   and electrocardiography abnormalities 
RenalAdultsSufficientDecreased glomerular filtration rateYes, < 5
 ≥12 years   
 ChildrenLimitedDecreased glomerular filtration rateYes, < 5
 <12 years of   
Reproductive andAdultSufficientWomen: reduced fetal growthYes, < 5
development  Men: adverse changes in sperm parametersYes, ≥ 15-20
   and increased time to pregnancy 
  LimitedWomen: increase in spontaneous abortionYes, < 10
   and preterm birth 
   Men: decreased fertilityYes, ≥ 10
   Men: spontaneous abortion in partnerYes, ≥31
  InadequateWomen and men: stillbirth, endocrine effects,Unclear
   birth defects 
 ChildrenSufficientDelayed puberty, reduced postnatal growthYes, < 10
  LimitedDelayed pubertyYes <5

Google Scholar Search Results For "Lead Poisoning" and Multiple Diseases: