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Putting public health concerns on the map

When Hilary Godwin joined the School of Public Health’s faculty in 2006 and was preparing to teach an introductory environmental health course for the first time, she conducted an informal survey of faculty as well as specialists working at the Los Angeles County Department of Public Health and other agencies.
What was the one skill, she wanted to know, that would be most important to teach students as part of their introduction to the field?
The answers she got pointed to one area of expertise — geographic information systems (GIS), the computer-driven system that allows researchers to capture, analyze and present data that’s linked to a location on a map.
Today, GIS has become an indispensable tool to urban planners, social scientists, biologists, geographers and others, but no more so than to public health researchers who are using it to gather life-saving information to assess the impact of everything from pesticides and air pollution to fast-food restaurants on your health, based on where you live and work.
But GIS is not just invaluable as a tool for analysis. It's become a powerful communications medium that can put complex data into a form that’s meaningful to community-based groups and policymakers.
“Often in public health we have very complex data sets, and maps can be much more powerful than technical graphs for conveying the meaning you’ve gotten from that data to different stakeholders,” explained Godwin, currently the school’s associate dean for academic programs.
Environmental epidemiologist Beate Ritz
Seeing is believing
“It goes back to the expression that a picture is worth a thousand words,” said environmental epidemiologist Beate Ritz, professor and vice chair of the Department of Epidemiology. She uses GIS to assess the potential health impacts of exposures to pesticides, air pollutants and other health threats. “If you can show on a map that people in proximity to roadways are at greater risk of negative health effects from pollutants, or that where there is poverty there are more liquor stores and no green spaces, it makes a much stronger case.”
Most recently, Ritz studied the dangers of ultraviolet radiation from the sun. “We’re interested in both time and space data,” she explained. “We take into account when people lived where, and what the exposures were at those times. It’s quite complex, but without that complexity, you can’t get an accurate assessment.”
Ritz goes so far to say that all the important discoveries she has made would have been less likely – and in some cases not possible – without GIS. In the mid-1990s when Ritz was analyzing pollutant exposure estimates over time and space without the use of computerized mapping software, crunching the numbers took her and her team as long as two years. With today’s GIS technology, the same type of task takes two to three days.
A pesticide map from a study done by Ritz assesses how much of a specific pesticide was applied on a crop within 500 and 1,000 meters of a residence in a specific year.
Mapping layers of complex data
“The brilliance of GIS is it allows you to take a coordinate in space and stack all sorts of information on it,” said Richard Jackson, professor and chair of the Department of Environmental Health Sciences. “When you do this across many individuals over large spaces, you get a robustness to your data and the ability to look at questions in ways you would miss with crude geographic identifiers such as state or ZIP code.”
When he served as director of the Centers for Disease Control and Prevention’s National Center for Environmental Health, Jackson said, he pushed to make GIS a “common language” for the agency’s environmental epidemiologists. Since then, the ranks of GIS supporters have swelled.
The use of maps to analyze and present spatial information in public health is not a new strategy. The practice, in fact, can be traced as far back as the mid-19th century and the work of Dr. John Snow, a physician who helped to pioneer the field of epidemiology with his response to London’s deadly cholera epidemic.
With the aid of a hand-drawn map on which he superimposed the locations of cholera deaths and public water supplies, Snow concluded that a contaminated communal water pump was the culprit. Removing the Broad Street Pump proved a turning point in the fight against the epidemic. As a testament to Snow’s pioneering work, Ralph Frerichs, now professor emeritus of epidemiology at the school, used GIS to create maps of London in 1859 tied to a history of Snow’s work.
Associate Professor May C. Wang uses GIS maps to analyze how access to supermarkets, convenience stores and other food-related businesses affects the risk of obesity in neighborhoods.
In the 1990s, GIS was introduced in public health most notably through maps plotting cancer rates in the United States and Europe. Today, researchers continue to use it to show spatial patterns of specific diseases to mobilize affected communities or to trigger investigations into why diseases might cluster in certain geographic areas. But its applications have broadened.
GIS has become an important ally for infectious disease epidemiologists such as Anne Rimoin, assistant professor at the school, who has used it to examine potential associations between ecological factors and the spread of monkeypox.
Jackson and others are using it to study the health impact of having green spaces and bike routes in communities. Researchers are also using GIS to display the density of convenience stores or fast-food restaurants in certain neighborhoods to show potential associations with poor health outcomes. “It’s like having a microscope with finer resolution — it enables you to see things you might otherwise miss,” Jackson said.
May C. Wang, associate professor of community health sciences is employing GIS to examine how a neighborhood’s food environment affects the risk of obesity in low-income pre-schoolers. “With GIS, we can see the specific geographic areas where healthy food is lacking, along with the effects this lack of access has on early childhood obesity risk. That can make a powerful case to policymakers,” Wang said.
From dental care to cancer screening
The UCLA Center for Health Policy Research, which conducts the state’s largest state health survey in CHIS, uses GIS for other kinds of analyses. Researchers at the center have mapped characteristics of dentists along with data on access to and affordability of dental care. Another project employs the mapping technology to show the relationship between distance of Asian American populations to community clinics and rates of breast and cervical cancer screening.
This map of Contra Costa County, Calif,, combines data on fast-food restaurants and other food establishments with census-tract data on household income.
In 2008, the center mapped concentrations of fast-food restaurants in neighborhoods along with obesity and overweight rates. Its widely reported “Retail Food Environment Index” prompted, among other things, a moratorium on the construction of new fast-food restaurants in South Los Angeles.
Maps for school readiness
Mapping can also bolster community planning efforts. The Center for Healthier Children, Families and Communities, led by Dr. Neal Halfon, is working with local communities to identify early childhood needs through
Dr. Neal Halfon
an initiative called Transforming Early Childhood Community Systems. They are using mapping technology and a tool, first developed by researchers in Canada, to measure key factors known to affect school readiness: physical health and well-being, social competence, emotional maturity, language and cognitive development, and communication skills and general knowledge.
Using data collected by kindergarten teachers with health, economic and other data on resources, these researchers are helping local communities map their needs and service gaps by neighborhood. Halfon’s group piloted the system in Orange County, and, with funding from the Kellogg Foundation, is now implementing it in 14 cities across the country.
“Mapping shows where the needs are in much richer detail,” Halfon said. “It’s been a game-changer as a way to facilitate community engagement, measurement, and the mapping of resources and assets.”
A longer version of this article appeared originally in UCLA Public Health magazine.
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