Lead

After Katrina, many of us were concerned about the environmental health risk related to returning to the city we love. Testing by the Environmental Protection Agency and independent consultants indicated that after the storm elevated levels of arsenic, lead, mold, diesel organics, and polycyclic aromatic hydrocarbons (PAH’s) were found in flooded neighborhoods throughout the city. Government testing, analysis and monitoring continued throughout the city until late December when the Environmental Protection Agency deemed the city “safe”. With respect to lead and arsenic, this designation of “safe” is based on comparison to pre-Katrina contamination levels. Studies by Xavier University expert Dr. Howard Mielke indicated that prior to Katrina, 20-30% of inner-city children had elevated blood levels above Centers for Disease Control (CDC) recommended target for elimination (10ug/L). A ug/L is a microgram or one-millionth of a gram per liter. For example, a Bic plastic pen cap weighs about one gram. For the entire city, the rate of elevated blood levels (above 10ug/L) in children was 14%.

When testing soil pre-Katrina, Dr. Mielke found that ten census tracts spread through Bywater/St. Claude, Treme/Lafitte, and Central City/Irish Channel neighborhoods had median soil levels greater than 1000 mg/kg. Post-Katrina, lead concentrations exceeded Environmental Protection Agency and Louisiana’s Department of Environmental Quality’s soil screening level for lead (400 mg/kg) in 57 of 147 composite samples collected in the areas where lead was previously detected in the samples collected in Fall 2005 . Soil screening levels are used to identify and define areas or concern, but do not alone trigger the need for federal response actions or define “unacceptable levels” of contaminants.

BACKGROUND

Although lead is a naturally occurring metal found in the Earth’s crust, most of the high levels found in the environment are due to human activity. The greatest increase has occurred between 1950 and 2000 with the increasing use of leaded gasoline worldwide. In the United States, lead additives were phased out in the 1980’s and leaded gasoline was banned for automobiles in 1996. This phase-out dramatically decreased the amount of lead released into the environment through vehicle exhaust). Historical sources of lead also include lead-based paint, canned foods (lead in cans), smelting, pesticides, and lead water pipes. Smelting is a process in which metal is produced from ore. In this case, lead smelting produced lead for batteries and other lead based products. Once lead is in the air, it can travel long distances and once lead is in the soil, it sticks to soil particles and remains in the upper layer of the soil. Currently in the United States, lead and lead alloys are most often used in the production of batteries.

HEALTH CONCERNS

Lead that is inhaled enters the lungs and then is quickly distributed to other parts of the body through the blood. The amount of lead absorbed when ingested depends on a number of factors including your age, when you ate your last meal, and how well the particles dissolved in your stomach juices. Through the blood, lead is distributed to the kidneys, liver, and bones. Lead often accumulates in the bones and teeth. Long-term exposure in adults may result in elevated blood pressure, gastrointestinal effects, anaemia, and kidney problems.

Children are most vulnerable to lead exposure for behavioral, physiological, and developmental reasons. Children are more likely to put their hands and other objects in their mouths than adults and the very young are more likely to be exposed to lead on the floor when crawling. Due to their size, children consume relatively more air, food, and water than adults therefore children are likely to absorb greater proportions of lead. Children absorb about 50% of ingested lead compared to adults who absorb 6%.

For children, long-term exposure has severe consequences on the central nervous system and intelligence. Declines in scores range from 2.6 to 7.4 IQ pts. Many studies have indicated that low levels of lead exposure below, at,or just above the CDC elimination target have an impact on intelligence quotient (IQ) scores. Currently, the CDC is focused on eliminating elevated blood lead levels (10 ug/L) in children by 2010.

WHAT DOES THIS MEAN FOR US

As we rebuild, long-term lead exposure at multiple levels is a serious concern. Many of us are in the process of gutting and restoring historic homes painted in lead-based paint. The EPA has provided recommendations for reducing the risk of lead poisoning and exposure during this process. Highlighted in these recommendations is the wearing of a NIOSH certified respirator, wearing protective clothes, using wet sanding equipment, and spraying surfaces with water to control the spread of dust.

We also need to take extra precautions to ensure that the paint that flakes off does not end up in the air or the soil. One way to accomplish this is by covering indoor surfaces and yard areas 5 ft (for single story homes) from the house with thick polythene plastic (6 mil) during rebuilding. Also require contractors to not use power or dry sanding methods on homes built before 1975. If you live on an existing property with high levels of lead or if you are purchasing a new home, especially with young children, it makes sense to consider the soil lead levels in the yard and remediate them.. There are large and small scale options for lead remediation including the planting sunflowers, adding organic matter to garden plots, and covering your lawn with a layer of topsoil and then planting grass seed. A large-scale option studied by Dr. Mielke first uses soils from the Bonnet Carre Spillway to cover yards throughout the metropolitan area and then plants grass seed mixed with water and fertilizer. More information on the feasibility of this option studied by Dr. Mielke is found here.

Children’s exposure to lead in our community has long-term consequences for the vitality of the city and the region. Prior to Katrina, regular screening of children living in certain areas of the city was often conducted by pediatricians and the Orleans Public Health Office. If you are concerned about lead poisoning of yourself or your children, you can ask your physician to conduct a lead blood level test. Either house by house or through city-wide efforts, this is an opportune time to attempt to reduce lead exposure in children of the Greater New Orleans area.

References 

Agency for Toxic Substances Disease Registry
http://www.atsdr.cdc.gov/cabs/lead/leadcabs_definition.html

EPA
http://www.epa.gov/iaq/homes/hip-lead.html

Mielke, Howard W., Eric T. Powell, Christopher R. Gonzales, Paul W. Mielke Jr.,Rolf Tore Ottesen, and Marianne Langedal, "New Orleans Soil Lead (Pb) Cleanup Using Mississippi River Alluvium: Need, Feasibility, and Cost"

Environ. Sci. Technol., 40 (8), 2784 -2789, 2006. 10.1021/es0525253 S0013-936X(05)02525-3
Web Release Date: March 10, 2006

NRDC
http://www.nrdc.org/health/effects/katrinadata/sedimentepa.pdf