How were the data for the Tracking Network chosen?

Health and environmental experts from states, cities, and other agencies helped CDC develop the indicators and measures you will find on this site. These decisions were based on many factors including priority for state and local health departments, priority for CDC, and whether or not data were available for a particular topic.

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How can we use environmental epidemiology to study disease patterns, trends and clusters?

We can measure some health problems by identifying the number of persons who have a particular disease or illness. We can also measure or estimate whether those persons have come in contact with an environmental hazard such as lead based paint in homes or arsenic in water. We can compare the number of persons who have a problem to their potential exposure to determine if there is a relationship. We can also study the same kinds of diseases or illnesses in people who have not come in contact with an environmental hazard to see if the numbers are different or the same.

Tracking is one of the tools used to monitor trends in environmental public health. The term describes how we collect data, interpret it, and report it.

In environmental public-health tracking, we examine trends of environmental hazards, exposures, health conditions, and groups of people. We do this for single and combined data sets. Surveillance information can be displayed in different ways such as maps, charts, or tables.

What can surveillance tell us?

Tracking is an important tool in environmental public health. It can be used to:

• Respond to questions from the public about environmental hazards, exposures or health conditions
• Identify patterns and trends that are not normal
• Develop or assess public health programs, rules, or policies
• Identify problems with data and work to improve them
• Explore connections among environmental hazards and health outcomes
• Produce ideas and plans for research
• Provide data for studies and investigations.

What can surveillance NOT tell us?

Tracking alone usually cannot specify whether something in the environment is causing a disease or health condition.

Scientists often use tracking information to determine trends and patterns and whether more research is needed. For example, a map that shows how often a disease occurs can be a starting point for more investigation. The kinds of questions tracking data can help us answer include:

• Are rates higher in a certain age or race/ethnicity group? Does the pattern vary by age or race/ethnicity group and by where people live or work?
• Are disease rates in cities different from rural areas? What about areas with higher or lower income or education?
• Do disease rates change over time? Do rates vary from year to year or because of the season?
• What do we know about issues that influence this disease from other research? How do these issues vary from area to area and over time?

The answers to some of these questions may help us understand why some areas have higher disease rates than others. Or, they may help determine where we need to do more work.

Environmental public health tracking uses different types of data to help examine information about the environment and human health. The Tracking Network contains data on some health effects, environmental hazards, exposures, and some other data.

Health Effects

Information is collected on an ongoing basis for surveillance of many health conditions. This information is compiled into tables, maps, and reports, and updated over time. Data are then displayed for a state as a whole, or by county or ZIP code. In some cases, links about how data are collected, presented, and checked for accuracy are included.

Not all data sets are developed for surveillance. Some are meant to be a record of births and deaths or to track hospital use. The way data are collected and presented might affect estimates and comparisons when they are used to estimate disease rates or track trends across the state.

Health data alone will provide only a little piece of information about how an illness may be related to environmental hazards or exposures. Most county and ZIP code maps and tables provide only a person's address. This information tells very little about how a person may have come in contact with environmental hazards. Many diseases, like cancer, take a long time to develop. So, exposures that occurred many years before would likely be more relative to the disease. Those exposures might not be related to a person's residence when they are diagnosed with a disease. This is one reason why connecting environmental problems and health problems can be difficult. To conduct environmental public-health tracking, health data must be compared with other information such as hazard data, exposure data, and other data.

Environmental Hazards

Environmental hazards are chemicals and toxins that can cause harm. An example of a hazard is lead paint in the home or particulate matter in outdoor air. The presence of a hazard does not necessarily mean that health problems will occur but it may cause a disease or other health problem.

Environmental hazard data are key pieces of the Tracking Network. Hazard data are collected by many agencies and include data from monitoring air, water, and soil. Environmental hazard data also include information from estimates, calculations, and facility reports. An example of hazard surveillance is air-pollution monitoring.

Exposure or Biomonitoring data

Exposure is contact with some contaminant or harmful substance. Exposure data can indicate the levels of chemicals, such as blood-lead level in a person. We collect data about chemicals by analyzing a person's blood or urine. Exposure data are also known as biomonitoring data. These data cannot tell you how a person was exposed to a contaminant. The level of contaminant in a person's blood or urine alone does not indicate that the contaminant caused their disease. Advances in testing methods allow minimal levels of contaminants in a person to be measured. More research is needed to determine which levels of contaminants are safe and which result in disease. Learn more about biomonitoring.

Other Data

Other data about the population enhance exploration of potential influences and risk factors for diseases or other health outcomes. For example, census data can provide information about a population’s income, race, or occupation. These factors might play a role in the number of cases of a disease in a specific area. The Tracking Network includes 2000 census data provided by the U.S. Census Bureau.

Is personal health information included in the Tracking data?

No. Data that could be used to identify an individual person is not shared with CDC for the Tracking Program. We follow all of the laws and policies that protect the privacy of health records and other personal information.

What are data privacy and confidentiality?

For the Tracking Program, data privacy means that health data will not be used for anything other than the specific public health reason it was shared.

Confidentiality means making sure that health information is only seen by people who are authorized to have access it.

How do data privacy laws affect tracking?

Laws that protect privacy are very important for the Tracking Program. State and federal laws that protect health data also help shape what information will be available on the Tracking Network. Protecting privacy and identities is very important. This balance not only provides enough information to make the data useful for public health but also protects private details about a person's health.

It is getting easier for health information to be shared by computers. This has many benefits for health care and public health and will help us do our jobs better. It is very important to treat this information with respect and protect it to ensure its privacy. Finding the right balance between sharing data that will help protect public health and being sensitive to a person's right to privacy can be difficult. However, many state and federal laws exist that help us work with our partners to make the Tracking Program useful.

What you find today is only the start of what the Tracking Network will become. New data and new features will continue to be added.

New data will include

• Additional census information
• Additional data on ozone and particulate matter
• Average daily number of hospitalizations for asthma and heart attack by month for Tracking states
• Cancer incidence for eight states
• Data for birth defects prevalence and carbon monoxide poisoning mortality from Tracking states
• Prevalence of legislation for mandating carbon monoxide detectors in homes
• Reproductive outcomes such as low birth weight and preterm birth

New Features will include:

• Ability to see an additional measure on the same screen
• Advanced viewing options
• Additional data-aggregation options
• Enhanced mapping capabilities
• Enhanced metadata
• Pre-designed "Quick" Reports