LEAD CONTAMINATION:

A RISK ASSESSMENT FOR

DOUGLAS COUNTY

Lauren Shaprio

UNO, Geography Department

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INTRODUCTION

Risk Assessment is the process of estimating the possible harm to human health or the environment when potentially hazardous materials remain on a site. Risk assessments are being used more frequently as a tool to meet regulatory requirements, characterize sites, identify remedial needs, assess remedial alternatives and select a remedial action. Risk assessments are used in all types of areas from International Business Environment Assessment, Investment, trade and risk analysis, to Political Risk Assessment and Management. Another aspect of risk assessments are Personalized Health Risk Assessments. A GIS provides the tools to integrate all of the risk categories systematically for the identification of problematic regions. For example, a lead contamination risk assessment can use data from the U.S. Census and local environmental quality data, to map relevant variable individually at local geographic scales. Then an integrative function (sum, weighted average) can then be specified to combine all of the variables into a single predictive model. Lead contamination is still a major concren for most cities, even though lead has been phased out of paint and gasoline for some time now. Lead is a perfect candidate for a risk assessment. A total of 17.6 million children are exposed to lead at toxic levels, either through lead based paint or gasoline(ATSDR 1988).

Lead is an element found throughout the environment in the earth's crust and from processes initiated by humans. It is found in the air, food, water, dust and soil. "Lead is an environmental toxicant that may seriously affect the nervous, hematopoietic, endocrine, renal and reproductive systems" (Health Department; Mortality and Morbitity). Lead exposure in young children is a particular hazard because children absord lead more readily than adults do and because the developing nervous systems of children are more susceptible to the effects of lead. Lead contamination is a deemed a priority for several reasons, among them are; Lead is a toxic heavy-metal that does not break down or decompose. Once released into the environment it persists, and can accumulate. Much of the estimated 330 million tons of lead that has ever been mined still remains, largely in the form of soil and dust contamination. Inhaled or ingested lead accumulates in the body, so even low-level environment exposure over time, can produce serious adverse health effects. It is these reasons why there is an urgent need for a study like this one. According to the CDC, Childhood lead poisoning, although widespread, does disproportionately affect low income, minority children. Lead poisoning is a preventable disease which can be combated and effectively eliminated through detection and intervention. The most desirable approach would be to screen entire communities for lead overexposure. However, it is likely that some communities will not have sufficient resources to implement such programs. Most communities should be able to screen a portion of the population at risk, so a strategy for identifiying those problem areas is needed. An effective starting point is to create a risk assessment. A risk assessment can point out potential areas for contamination, using specific criteria. Once a risk assessment is created, health workers can then go in and demand that these areas need to be tested first, they are the most likely to be at risk.

Douglas County, Nebraska like any other county in the U.S. has the potential for risk. Although companies like ASARCO are no longer in business, the negative effects are still present. Using demographic data gathered from Wessex ( a series of CD's with census data for the entire U.S.) and outlined by the CDC, and the Health Department and State Lead Department of Nebraska, a risk assessment for Douglas County was created to show the areas of highest risk.

 

To see Final Risk Assessment Map Click Here

 

 

 

 

METHODOLOGY

As an undergraduate student I had the opportunity to work on a project about Lead Contamination in Tampa Bay, Florida. Also, my thesis topic as a graduate student is dealing with Lead Contamination in the soils of Belize City, Belize, so consequently, I already possess some background knowledge on the subject. However, through this class I have been given the chance to work with the Douglas County Health Department and the State Lead Department, who in turn, have given me some ideas as to the variables needed in order to begin the risk assessment. In this project as compared to other work I have been involved in there is no outside testing in the field. All of the variables needed were provided by census data.

The first step in this project was to assess the variables needed in a risk assessment for lead contamination. According to the Health Department, the people that are of greatest risk are children under the age of five, who are among some type of minority group and whose families fall below the poverty level (the level that the Health Department uses is below $12,500).

The next step was to access all of this information through Wessex. Wessex was formed in 1983 as a spreadsheet/database design and consulting firm. In the 1990's however they released the first version of Pro/Filer, which is a windows based product that gives the user access to data gathered in the 1990 census. These CD's contain the demographic needed to begin this project. However, before a table can be built from all of this data, a shape file of Douglas County by Block group was downloaded. This created a base map which to work from and an attributes table where the demographic information could be joined to. Block groups are a small area made up of blocks delineated by state and local officials in conjunction with the Census Bureau. Block groups were designed to contain 400 housing units, although they typically averaged 452 to 1,100 people. Block groups do not cross census tract boundaries. After the shape file was downloaded, it was time to create the demographics table. On the Wessex CD's, the information was not available in three nice and neat columns, those would have to be created later. The actual table was created with a column of each individual age group by year. For example, a column could be created of children under the age of 1 yrs. old, a column of children from 1 to 2 yrs. old, a coulmn of children from 2 to 3 yrs. old and so on. Next the minority groups were broken down into categories. A column was made for Blacks, American Indians/Eskimos, Asian Pacific and a column for other race. Also the income levels under the poverty mark were divided up into under $5,000, $5,001 to $10,000, and from $10,001 to $12,500. The final column made might have been one of the most important. A column of block group id numbers was added. In the end, this will allow a join from this table to the shape file that was made.

Once the table was created and downloaded off the Wessex CD's, the table could be taken into excel and manipulated. There were a total of 440 blockgroups to work with.

The first step in Excel was to merge several of the columns together to create a column for the total number of children under the age of 5.

WESSEX DATA

Table1

 TOT_UND1

 TOT_1AND2

 TOT_3AND4

 TOT_5

UNDER_5 

 0

 0

  0

 0

 0

 6

 16

 14

 14

 50

 12

 29

 30

 16

 87

 13

 17

 27

 10

 67

 10

 27

 29

 22

 88

Snap shot of larger database, used soley for presentation

Presentation Outline

 

The next step was to take all of the minority groups and create one column that contained all of the minorities as one. Hispanic is considered to be in the other category. Also AMINESKAL means American Indian and Eskimo, ASIANPACI, means Asian Pacific.

Table2

 BLACK  AMINESKAL  ASIANPACI  OTHERRACE  MINORITIES
 58  0  51  0  123
 9  0  23  0  32
 17  5  0  18  58

Snap shot of larger database, used soley for presentation

Presentation Outline

After merging the columns of income together (as in step #2) to get a total number of people under the poverty level, the next thing to do was to make each variable, children under 5, minorities, and number under the poverty level a percentage of the total people in each block group.

Table3

 %UN5  %MIN  %Poor
 7  1  1
 8  0  1
 5  5  0

Snap shot of larger database, used soley for presentation

Presentation Outline

The final step in Excel before ArcView was to rank each variable. The lowest value for each category recieved the lowest ranking and the highest value recieved the highest ranking and where the values were the same, they were added together and averaged. Then each column of ranked values was added together and averaged to get a total risk value for each block group.

Table4

 UN5/RANK  MIN/RANK  POV/RANK  RISK
 4  24  17  15
 60  24  17  33
 98  24  54  59
 98  96  17  70
 98  24  89  70

Snap shot of larger database, used soley for presentation

Presentation Outline

After the database was completed in Excel, then next software to be used was ArcView, "ArcView is a desktop geographic information system that allows the user to organize data, ask questions of data using digital maps, and create new geographic data from original data"(ESRI). Once the program was opened the first step was to open up the shape file created from Wessex. This was done by clicking on the views icon and selecting add theme. After adding the shape file a legend marker will appear in your View window. Click on the box in that legend marker and a proected image of the Douglas County by block groups will appear in your View window. This theme can be turned on and off by clicking on this box. A projection for this base map must now be selected. In the project window, the views icon was selected Under the view menu, properties was selected. The projection button was clicked on and projection of the United States was selected as the category and the type that was selected was Albers Equal Area. This displays the map on a projection instead of a normal ArcView display file.

In order to display the risk value information, it must be joined to the attribute information of the shape file. To do this the table option under theTheme menu was selected. This displayed the attribute table for the shape file. The next step was to select add table under the main project window. This allows for the table created in Excel to be brought in. Now that the two tables are in view, the column for block group was highlighted for each table, making sure that the attributes table was the active table, and the join button was selected. This joined the two tables into one and added all of the values created in Excel to the shapefile. The Legend Editor was then open again and graduated color was selected and the map was classified by risk value and normalized by nothing. Natural breaks were selected and a standard color scheme of yellow to orange to red was chosen. However, there was not enough differentiation between the darker colors so a highest risk value color of black was selected. This ensured that the reader would have no problem distinguishing between risk categories. For this first map the last step in ArcView was to go to the layout option under the view menu and construct the final amp output. After all of the essential map components were added (i.e. north arrow, legend and title) and appropriately placed, the map was exported as a new postscript (or eps). Several maps were created for this project. Three separate maps were constructed to display the individual variables that were used. Also, the original view was manipulated in such a way that the highest risk areas were the main focus point of the second map created. Once all of these maps were created they too were exported as EPS maps.

The six maps that were created were taken then into Adobe Illustrator to add the final touches. Road names were added to several of the maps to create reference points. This allows the reader to associate him/herself better with the area. The maps were then saved as either PDF or Illustrator files dependent upon what the project called for. The PDF file was printed directly to Gaia and the Illustrator files were taken into Adobe Photoshop and converted into Compuserve GIF's.


Figure3

Click on smaller maps for detail

 

 

Presentation Outline

Results

Figure2

 

Presentation Outline

The results of this project suggest that the areas for the highest risk are to the North of Dodge Street and to the East of 72nd Street. This areas is very high in African American Minorities. There is also a small number of potential risk areas to the South of Dodge along 24th Street. This area is known for its large hispanic population. Which makes sense when, according to the ATSDR, "In the United States 60% of the African Americans and Hispanic Americans live in communities with higher than average levels of toxic contamination" (ATSDR 1988). The results of this analysis due provide a clear picture of the geographic distribution of potential risk areas for lead contamination, however, it is worth noting that this analysis is based only on potential risk and not absolute contamination. It is therefore expected that the risk areas will either significantly increase and be more geographically widespread or will decrease due to the small amount of pollution sources in the area.

 

Conclusions

Most risk assessments are subject to scientific controversy. In the areas where pollution is regulated the standards are based on the assumption that people are fairly similar in their susceptibility to toxins. We now know however, that socioeconomic characteristics play a pivital role in the effects of pollution, and as seen by this project, environmental health hazards are acknowledged to be more severe in low-income neighborhoods. The children in these areas tend to lack the calcium and iron in their diets that helps to fight the absorption of lead in their bodies. As you can see from this chart created by the ATSDR, lead contamination can be a huge problem for children as well as for some adults. A risk Assessment such as this can be the starting point for any lead abatement project. This particular risk assessment will be used in a future project, by overlaying actual elevated blood levels of children in Douglas County, to the final risk assessment map. In conjunction with the Douglas County Health Department, this future project will be able to quantify how effective a risk assessment can be by measuring up predicted risk areas to actual risk areas.

Related Links:

Childhood Lead Contamination

Office of Pollution Prevention and Toxic, EPA

Impact of Lead Contaminated Soil on Public Health


References

  • Wartenburg, Daniel. 1992. Screening for Lead Exposure Using a Geographic Information System. Environmental Research. 59, 310-317.
  • Bocco, Gerardo and Sanchez, Roberto. 1997. Indentifying Potential Impact of Lead Contamination Using a Geographic Information System. Environmental Management. Vol.21, No.1, 133-138.
  • EPA. http://www.epa.gov/
  • Agency for Toxic Substances and Disease Registry (ATSDR). 1988. The Nature and Extent of Lead Poisoning in Children in the United States: A Report to Congress, July.
  • Agency for Toxic Substances and Disease Registry (ATSDR). 1990. Case Studies in Environmental Medicine: Lead Toxicity.
  • Agency for Toxic Substances and Disease Registry (ATSDR). 1992. Toxilogical Profile for Lead. ATSDR/TP-88/17.
  • Centers for Disease Control(CDC) 1991. Preventing Lead Poisoning in Young Children. October.

  • Presentation Outline