Policymakers must pick and choose from an array of important priorities in which to invest their time, energy, and funding. While framing the expected health benefits from reducing lead exposure in terms of dollars can appear crass, it is an important tool to help compare priorities. And it is less abstract than health endpoints such as blood lead level, IQ points lost, or risk of death from cardiovascular disease.
Fortunately, EPA has provided important tools to quantify the societal benefits of reducing lead exposure. We will explore those tools in a series of blogs, starting with EPA’s All Ages Lead Model (AALM) and moving to the benefits that the agency has rigorously quantified.
Figure 1. Example of an output from AALM
What Happened
Last year, EPA released version 3 of its All Ages Lead Model (AALM) after incorporating recommendations from its Science Advisory Board in 2020.1 The latest version is impressive and more user-friendly than its 2019 predecessor.
The AALM “rapidly estimates the effect of exposures on lead concentrations in tissues of children and adults; can assess exposures of a day or more, as well as chronic exposures; and can be applied to specific individuals or to groups of similarly exposed individuals.” It is a flexible model that can estimate blood lead levels from birth to 90 years of age that result from exposure to lead in air, water, food, dust, soil, or other sources. It can model exposures that occur on various days of the week and at various ages.
The AALM is more versatile than EPA’s Integrated Exposure Uptake Biokinetic Model for Lead in Children (IEUBK) because it: 1) covers people older than 7 years of age; and 2) allows for exposures that vary during days of the week or times shorter than one month to be evaluated with results shown for each day. While the AALM does not estimate blood lead levels in a developing fetus, it can be used to estimate a maternal blood lead level. Infants are born with a blood lead level that is about 0.9 of their mother’s.
Why it Matters
The scientific consensus is that there is no known safe level of lead exposure. The greater the lead exposure, whether in terms of the duration or the daily intake, the greater the predicted harm.
Predicting that harm is complicated because lead accumulates in bone, blood, and other tissues in the body. Calculating that accumulation requires sophisticated computer models based on how the human body absorbs, distributes, metabolizes, and excretes lead.
The AALM does that by converting the exposures provided by a user in a Microsoft Excel spreadsheet into blood lead levels.2 The next step is to estimate the health impacts that are likely to result from those blood lead levels, which is the topic of future blogs.
Our Take
By having AALM rigorously evaluated by its Science Advisory Board and making the model publicly available in a relatively user-friendly, versatile format, EPA empowers people to quickly and credibly evaluate various interventions and policies that reduce lead exposure at all stages of life.
The AALM is particularly important because it enables users to:
- Run the model without EPA’s support, a key issue given the recent cutbacks at the agency;
- Gain insight into health impact from adult exposure given the evidence that lead increases the risk of dying from cardiovascular disease and can affect the health of a developing fetus;3
- Consider not just exposure to lead in dust but also from food, air, and consumer products;
- Consider the next step of calculating the socio-economic effects from those exposures.
We encourage everyone to download the program and Users Guide. Below are some instructions to get users started.
Quick Guide to Setting Up and Running AALM
To set up the program on your computer:
- Go to https://github.com/USEPA/AALM
- Click on green “<> Code” button.
- Select “Download ZIP” from the pulldown menu.
- After downloading the zip file, copy the “AALM-main” file to your computer.
- Go to the “AALMv3-0_PublicRelease” folder and then the “AALMv3-0” folder.
- Open the “AALMv3-0_030124” Microsoft Excel Macro-Enabled Worksheet. You may need permission from your network administrator to open the spreadsheet since it has macros.
To run AALM:
- Read the Users Guide, especially “Media Parameters” on pages 20-22.
- On “Simulation Control” worksheet, select which media you want to model and the number of exposures for each.
- Click on rust “Go to Media” button and enter details on “Media” worksheet.
- When ready, return to “Simulation Control” worksheet and click dark blue “Run Simulation” button. To avoid a dialog box, you may want to save the file under a different name.
- Be patient if running a complex scenario for an adult and get a cup of coffee or tea.
- When ready, the “Output Selection” worksheet opens.
- Click on dark blue “Explore Data” button to see results.
- On “Explore Data” worksheet, doublecheck the age range to be shown.
- If you make changes to the ages, you may want to click on grey “Update” button at the top right.
If you need help or have questions, EPA can provide technical assistance (see email at bottom of its AALM webpage) or reach out to Unleaded Kids’ Tom Neltner at tneltner@unleadedkids.com. We are hoping to develop a learning community of people using the tool and to show how to use it for common scenarios.
- EPA issued version 1 in 2005 and version 2 in 2019. EPA says the “AALM is an outgrowth of the Integrated Exposure Uptake Biokinetic Model for Lead in Children (IEUBK). IEUBK assesses changes in blood lead in groups of children up to 7 years of age, over periods of a month or more.” ↩︎
- As well as blood plasma, cortical bone, and trabecular bone. ↩︎
- The AALM does not estimate lead levels in a developing fetus. The AALM, however, can be used to estimate a maternal blood lead level. Infants are born with a blood lead level that is about 0.9 of their mother’s. ↩︎