How can
I see a full list of included data?
Follow the link from Build Your Own Map and scroll through
the layers.
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What is metadata?
Metadata is “data about the data.” Metadata is
all the information that will help you better understand the
data, and includes details about the quality, source, and content
of the data. The use of metadata is standard in the GIS industry,
and the methods for reporting metadata used here are the standard
developed by the Federal
Geographic Data Committee (FGDC) To access metadata, click
on the data layer you are interested in and the metadata will
open in a new window.
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The map displays the data as a
range. How can I get the actual numbers?
You can use the Identify tool and click on a specific town or other map
item to reveal detailed information.
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Why did you use these particular
data layers?
The primary objective of the pilot version of this application
was to make the Institute's original research on breast cancer
and the environment on Cape Cod publicly available. The secondary
objective was to enhance these data with other publicly available
environmental and public health data sets for MA. The data
included in this version of the application are primarily publicly
available data sets from the Environmental Protection Agency
(EPA), Massachusetts Geographic Information System (MASS GIS),
and the Massachusetts Department of Public Health (DPH).
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What data did you want to include
that you couldn't?
The purpose of MassHEIS is to bring together geographic data
on health effects and environmental pollutants so that potential
relationships can be explored by researchers and the public.
In the context of this project, environmental data are useful
if they can be used to estimate pollutant exposures or evaluate
relationships between human activities and environmental change
(e.g., how does drinking water quality relate to the land uses
within drinking water well recharge areas?). Health
data
are useful
if they are systematically collected, can be expressed with
reference to an expected frequency in the underlying population,
and can be shared on a scale that is relevant to variations
in pollutant exposures or demographic factors of interest.
The data currently included in MassHEIS are the most relevant
we were able to identify, but many of the included data sets
have limitations. Data on many environmental and health features
of interest are simply not available. For example, only limited
data are available on prevalence of learning disabilities and
autism; rates of many common cancers and health effects would
be more informative if mapped by census tract rather than by
town; and pollution monitoring data are extremely scarce. With
a greater state and federal investment in public health tracking,
more could be learned.
A few examples of data we were not able to obtain are described
below:
(1) Established risk factors for breast and other cancers, including
body weight, alcohol use, and tobacco use: These data are only available
for major metropolitan statistical areas in MA through the Behavioral
Risk Factor Surveillance System (BRFSS).
(2) Brownfields: A compilation of all brownfields in the state does not
currently exist. The MassDevelopment agency terms brownfields as "vacant,
abandoned, or underutilized industrial or commercial properties where
expansion, redevelopment, or improvement is complicated by real or perceived
environmental contamination and liability." MassHEIS does, however,
display a data set, the MassDEP Tier Classified Oil and/or Hazardous
Material Sites, pinpointing all the sites currently going through the
Mass. 21E regulatory clean up process.
(3) Pesticide application: Silent Spring Institute compiled detailed
historical data on wide-area pesticide applications across Cape Cod from
the 1940s to 1990. Comparable historical information for the rest of
the state has not been compiled, and no electronic, geographically-oriented
data on current pesticide applications are available in MA to map (although
certain land use categories may be assumed to involve pesticide use).
Other states, such as California, have pesticide application reporting
requirements and tracking systems that, if implemented in Massachusetts,
would allow mapping of all pesticide applications by registered applicators
for the entire state.
(4) Current data on modeled hazardous air pollutants: The EPA published
a national hazardous air pollutant model using 1996 data, but has not
published an updated version. New data would allow trend analysis and
comparisons with current patterns of respiratory health effects.
(5) Cases of Asthma: The BRFSS collects self-reported data on cases of
asthma but these data are only available for limited geographical areas.
Instead, we chose to map incidence of asthma or asthma-related hospitalizations,
because these data are available by town for each town in MA.
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Why do you include only Massachusetts?
Prompted by the breast cancer incidence rates that are 20%
higher on Cape Cod than the rest of MA, Silent Spring Institute
in 1994 began a long-term research program to investigate the
possible role environmental factors have on breast cancer incidence
on Cape Cod. Because Cape Cod is a fragile ecosystem, with
water resources easily affected by contaminants deposited on
the land surface or leached from wastewater, breast cancer
activists called for an investigation of the role that environmental
pollutants played in the long-term health of Cape residents.
As part of that study, Silent Spring Institute created a Geographic
Information System (GIS). GIS is a computerized database that
can be used to store, analyze, and display data, particularly
data associated with locations on a map.
HEIS is intended to provide public access to the integrated health and
environmental information gathered during the course of the Cape Cod
Breast Cancer and Environment Study and thus most detailed data are available
for Cape Cod. The secondary objective was to enhance these data with
other publicly available environmental and public health data sets available
for MA. The data included in this version of the application are primarily
publicly available data sets from the Environmental Protection Agency
(EPA), Massachusetts Geographic Information System (MASS GIS), and the
Massachusetts Department of Public Health (DPH).
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What is statistical significance
and why is it so important?
Statistical significance is a useful guideline in interpreting
research findings because it assesses the likelihood that results
are due to chance alone. Statistical significance is based
on a number called a "p-value." By convention, results
achieving a p-value less than 0.05 are called statistically
significant, which simply means that there is one chance in
20 that the finding is due only to chance. The traditional
cutoff for statistical significance of p less than 0.05 is
arbitrary, and an Standardized Incidence Ratio (SIR) that
approaches but does not attain statistical significance may
still be of interest.
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How accurate is the data?
Because the data come from a number of different sources,
the quality of the data can vary. Generally there are two components
to the quality of information in GIS. The first is the accuracy
of the geographic coordinates used to locate information relative
to its actual location . Second is the accuracy of the attributes
associated with the geographic point. The first component is
unique to GISs while the second component would apply to any
database. Different sources have different quality control
mechanisms. Most of the data included in MASS HEIS comes from
organizations with established quality control procedures and
it is important to refer to the original source when evaluating
data quality. As a quality control measure, all Silent Spring
Institute data were verified by a staff member who did not
participate in the data entry. By clicking on the data layer
you can learn about the sources of other data sets included
in HEIS and can follow the links back to the original sources.
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What are SIRs and why are they used rather than rates?
Standardized Incidence Ratio, or SIR, is a common tool for
monitoring disease rates. Incidence is the number of newly
diagnosed cases in a given location during a given time period.
An SIR compares the actual number of cases for a given place
and time to the number that would be expected based on cancer
rates in some comparison area. SIRs are usually written as
100 or 125 instead of 1.00 or 1.25. An SIR of 100 means that
the actual number of cases equals the expected number. An SIR
of 125 means that the actual number of cases was 25% higher
than expected. An SIR of 75 means that the actual number of
cases was only 75% of the expected number. For more information,
see our glossary.
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What are limitations of
the data?
The quality of inferences that can be drawn from the data
depend on the quality of the original data. Information in
HEIS depends on varying sources of data, methods of collecting
and organizing data, scales of the data, and completeness and
accuracy of historical records. In addition, Silent Spring
Institute has followed standard practice in not reporting cancer
information where fewer than 5 cases appeared in a particular
town or census tract in a particular time period in order to
protect the privacy of individuals. We also only included data
occurring with a high enough frequency to be meaningful when
mapped. For example, Institute researchers determined that
birth defects are not prevalent enough to map at the municipal
level, given that such data have only been reported to the
public for three years. In the future, it may be possible to
map birth defects by town by aggregating data over a longer
time period. To learn more about any particular data layer,
click on the data layer.
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What does -999 mean?
Where data was not available or censored, the value -999 was
substituted to clearly differentiate the record from those
with real data. Silent Spring Institute is invested in protecting
the privacy of individuals and has followed standard practice
in censoring town level cancer data rates where fewer than
five cases appeared in a particular time period.
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Why is some data displayed as
points and some as shapes?
Data for an area (e.g., town, census tract, county, or school
district) are represented by a color shade for that area. Data
related to a specific location (e.g., a factory) are represented
as points. Most of the health data is represented as shapes
and most of the environment data as points. Although the reported
observation (e.g., cancer rate) for a municipality appears
evenly distributed throughout the town, it may not be. Further,
though much of the environmental data are represented by a
single point or location on the map, that does not mean that
the impact of the facility does not reach further than its
immediate location. To protect privacy, health data that pinpoints
individual cases is generally not released. Instead, health
data are aggregated and displayed by census tract, block group,
or town level.
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How can I find out where
the data came from, how it was collected, quality control
methods, and other information?
Metadata, "data about the data" is information that
will help you better understand the data, and includes information
about the quality, source, and content of the data. The use
of metadata is standard in the GIS industry, and the methods
for reporting metadata used here are the standard developed
by the Federal
Geographic Data Committee (FGDC) Most data sets include
links back to their originating sources. To access metadata,
click on the data layer you are interested in and the metadata
will open in a new window.
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