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Contents
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Queries
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Injury Estimates
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Injury Rates
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Help
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Help With Queries
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The Query Screen
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Resources
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TECH INFO CONTENTS
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DATA SOURCE, DESIGN, & CASE DEFINITION
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ESTIMATES & ERRORS
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DATA ELEMENTS & REPORTS
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DATA SOURCE, DESIGN, & CASE DEFINITION
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Work-RISQS is an online data access system for NIOSH surveillance data on nonfatal
work-related injuries and illnesses treated in U.S. hospital emergency departments
(EDs). NIOSH collaborates with U.S. Consumer Product Safety Commission (CPSC) to
collect these data through a supplement to the CPSC National Electronic Injury Surveillance
System (NEISS). The occupational supplement is referred to as NEISS-Work.
The occupational injury and illness supplemental data are collected without regard
to consumer product involvement, whereas the CPSC NEISS data exclude work-related
injuries and illnesses.
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NEISS-Work is a national stratified probability sample of hospitals in the U.S.
and its territories that have a minimum of six beds and that operate a 24-hour emergency
department. Hospitals in the sample were selected from the approximately 5,300 rural
and urban U.S. hospitals after stratification by total annual emergency department
visits. Nominally, 67 geographically distributed sample hospitals capture work-related
injuries and illnesses every day of the year (note: the occupational injury hospital
sample is a subset (2/3) of the hospital sample used by CPSC for capture of product-related
injuries). All treated cases that are identifiable as work-related are captured
and information is abstracted from the medical record.
Each case is assigned a statistical weight based on the inverse probability of selection.
National estimates are obtained by summing weights for all cases or particular cases
of interest. Statistical weights are adjusted within a sample year to account for
hospital mergers, hospital closings or withdrawal from NEISS-Work (i.e., less than
67 hospitals reporting information), and incomplete reporting. Statistical weights
are adjusted annually based on the number of U.S. hospitals and their total number
of ED visits as determined by a census of U.S. hospitals one year prior to the data
year.
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Medical:
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Nonfatal injuries and illnesses treated in an emergency department
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Population:
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Civilian non-institutionalized workers
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Work:
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- Doing work for pay or other compensation, including arriving or leaving work but
on the employer's premises, during transportation between locations as a part of
the job (excluding commuting to or from home)
- Doing agricultural production activities
- Working as a volunteer for an organized group (e.g., volunteer fire department)
More detailed guidelines...
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Demographics:
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All workers without restriction by age, type of employer or industry (e.g., self-employed,
private industry, or government), or employer size
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- Injuries or illnesses to active duty Military, National Guard, and State Militia
- Injuries or illnesses to institutionalized persons including prisoners or mental
health patients
- Common illnesses (e.g., colds and flu)
- Routine drug and alcohol screening
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Revisits to the same ED for a previously treated injury or illness
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Work-related cases are identified from admissions information and emergency department
chart review by hospital coders. A workers' compensation claim is not required for
inclusion.
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ESTIMATES & ERRORS
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NEISS-Work is designed to produce national estimates and is not suitable for regional,
state, or local injury and illness estimates. A national estimate is obtained by
extrapolating the number of cases seen in the approximately 67 hospitals by using
the statistical weight of each case. The statistical weight varies depending upon
the size of the hospital and the number of patients typically treated in their ED.
In other words, each case captured in a sample hospital may represent 20 to more
than 100 cases seen in other U.S. hospitals. By summing the weights for similar
cases a national estimate is obtained for a specific demographic group, type of
injury, injury circumstances, or all injuries and illnesses. In Work-RISQS, national
estimates are expressed in thousands of injuries and illnesses for a given year.
For example, in 1998 there were an estimated 3,559.5 thousand or 3,559,500 occupational
injuries and illnesses treated in U.S. hospital emergency departments. Other surveillance
systems may produce different estimates.
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Because the NEISS-Work system is just a sample of all U.S. hospitals and does not
count every injury or illness treated in all hospitals, the national estimates may
be in error. However, because the sample was statistically selected, we can calculate
what the error due to sampling is likely to be. Each estimate produced by Work-RISQS
has confidence bounds listed. The error estimates are based on the 95% confidence
interval and are expressed as a value that should be subtracted from the estimate
to get the lower confidence bound and added to it to get the upper bound. For example,
in 1998, there were an estimated 3,559.5 thousand work-related injuries and illnesses
with 95% confidence bounds of ±605.1 thousand cases. In other words, we expect the
true value from this system is likely to be in the range of 2,954,400 to 4,173,600
injuries and illnesses. Simply put--there were about three to four million non-fatal
occupational injuries and illnesses treated in U.S. ED's in 1998.
The confidence bounds do not account for biases (nonsampling error) in the estimates
that arise from the way in which data are collected or defined, ability to identify
all work-related cases, or mistakes in data collection or coding.
The 95% confidence bounds are an approximation based on the classical formula for
variance of a total from a stratified sample. These confidence bounds are an approximation
of the general magnitude of error about an estimate and are not precise values.
The variance estimating formula currently used by Work-RISQS is:
Where:
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Number of strata in the sample during the given time period
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Number of hospitals in the sampling frame for stratum h
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Number of hospitals selected for the sample for stratum h
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Number of in-scope hospitals in the sample for stratum h
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Number of hospitals participating in stratum h for the given time period
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Number of occupational cases for a specific type of injury reported by hospital
i in stratum h for the given time period
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Weight of hospital i in stratum h
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The 95% confidence bounds, expressed as an amount to be subtracted or added to the
national estimate, are then calculated as:
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Where:
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Variance of the injury estimate x
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Injury estimate
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Effective with the December 2008 update to Work-RISQS a minor modification was made
to the variance calculation in the way that the number of reporting hospitals was
determined () for all data years. Previously, hospitals were included in
(an integer value) if the hospital reported for 7 or more months of the calendar
period. To minimize issues with negative variances,
is currently calculated as a fractional
value where
equals the sum of number of months that all hospitals within a strata reported during
the calendar period divided by 12 months. Thus, current confidence bounds may not
equal previously reported results, but the differences will generally be insignificant
or undetectable.
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The employment estimates used in Work-RISQS are derived from the U.S. Bureau of
Labor Statistics Current Population Survey (CPS) of
civilian non-institutionalized workers. Employment estimates are calculated for
Work-RISQS as full-time equivalent workers (FTE), where one FTE equals 2,000 hours
worked per year. The FTE estimates account for hours worked in all jobs reported
to CPS. At Work-RISQS, FTE estimates may be obtained by month, quarter, or year
for workers 15 years and older. Also, FTE estimates may be obtained by age group
or sex.
Volunteer workers are not included in CPS estimates, although they are included
in the Work-RISQS injury/illness counts. This creates a small, but insignificant,
bias in rate estimates.
Approximate standard errors are calculated for CPS employment estimates by using
parameters for selected demographic characteristics in a generalized variance function
provided by the Bureau of Labor Statistics (see for example, USDOL Bureau of Labor
Statistics Employment and Earnings Online, 2008: v.
55(1), 274-294). Parameters are independent of the time period selected within a
given year, although they may change from year to year. In the calculation of error
in the employment estimate, the selection of the variance parameters for the specific
year are chosen based on the appropriate employment characteristics. When multiple
characteristics apply for specific subsets of sex and/or age groups, the parameters
are chosen to provide the most conservative error estimate (i.e., the largest error
estimate). The errors generally decrease with longer time periods and when a specific
sex or age group < 20 yrs is selected. However, the errors resulting from these
calculations are only an approximation of the true sampling error and do not account
for systematic biases in the data.
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In workplace safety, the injury/illness rate is calculated commonly as the frequency
of injuries divided by the number of workers or the number of hours worked within
a specific time period. Work-RISQS only provides rates as the number of injuries
and illnesses per 200,000 hours worked (i.e., 100 FTE) for time periods of a month,
quarter, or year. A rate estimate query at Work-RISQS produces a table that includes
the number of injuries and illnesses treated in an ED (the rate numerator) , the
FTE (the rate denominator), the rate per 100 FTE, and the confidence bounds expressed
as a value to be added and subtracted from the rate value.
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The variance of the rate estimate is the pooling of the variances for the injury
estimate and the FTE estimate. In general, the variance about the injury estimate
is large with respect to the variance in the FTE estimate. The confidence bounds,
expressed as an amount to be subtracted or added to the injury/illness rate, are:
Where:
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Rate of injury/illness per 100 FTE
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Coefficient of variation of the injury/illness estimate
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Coefficient of variation of the employment FTE estimate
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DATA ELEMENTS & REPORTS
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Definition: Calendar year in which first emergency department medical treatment
was received.
Injuries and illnesses in Work-RISQS may be queried based on the date of first treatment
in a NEISS-Work hospital ED. The user may select data to query for one calendar
year at a time, beginning in 1998. Multiple years can not be queried simultaneously
within Work-RISQS.
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Definition: Calendar month in which first emergency department medical treatment
was received.
Queries may be made for cases treated in one or more months. The months need not
be consecutive. Injury estimates are based on the actual number of cases treated
within a calendar month. In the determination of injury rates, the numerator is
also based on the number of injuries treated within a calendar month. However, the
FTE denominator assumes that all months have 30 days.
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Definition: Inclusive range of ages of patients (in years)
Injured or ill workers are grouped by age ranges (typically a 5 year range). One
or more age groups may be selected. There are no age restrictions for cases captured
in NEISS-Work providing they meet the definition of a work-related case. However,
injury rates are not available for youth less than 15 years of age because data
on hours worked are not available. Age is unknown for a small proportion of cases.
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Definition: The distinction between male and female.
A worker's sex is indicated as male, female, or not stated. In any given year's
data, the number of cases with sex listed as not stated is very small (e.g., typically
< 0.01% of all cases).
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Definition: Construct for classifying people with similar biological, social,
and cultural heritage into four race groups (White, Black, American Indian/Alaska
Native, and Asian/Pacific Islander) and one ethnicity group (Hispanic or Latino)
as recorded on the emergency department chart.
Within the original NEISS-Work data, race and ethnicity of an injured worker are
collected as a two-part question. In the first part, race is coded as "white,"
"black," "other," or "not stated."
In the second part which is free text, other races may be described such as Asian
or American Indian or ethnicity may be entered such as Hispanic or
Latino. Because NEISS-Work hospitals do not collect race and ethnicity uniformly,
if they collect or report it at all, and the two-part nature of the NEISS-Work race/ethnicity
question, consistent reporting of race and ethnicity is not always achieved. For
example, a Hispanic patient might be indicated as: (1) white or black
with the free text blank (only race reported); (2) white or black
with Hispanic entered into the free text (both race and ethnicity reported);
and (3) as "other" with Hispanic in the free text field
(only ethnicity reported).
Within Work-RISQS, race and ethnicity were recoded under a single combined data
structure where Hispanic ethnicity was indicated preferentially as opposed to white
or black race. Thus, for the purposes of estimating injuries and illnesses, workers
who were identified as white or black and Hispanic or Latino were counted under
their Hispanic ethnicity. If originally race was listed as "other" and
the free text contained a country of origin or ancestry, those cases were recoded
to the race or ethnicity category predominant for the region (e.g., Chinese was
recoded as Asian and Mexican was recoded as Hispanic). Race was recoded as "not
stated" if the free text listed "Indian" without an indication that
the patient was American Indian or Native American. However, Indian was recoded
to American Indian if the NEISS-Work hospital where the case was seen generally
treated a large population of American Indians.
WARNING: Because of the problems outlined and others in the collection of race and
ethnicity information as well as missing information for approximately 20% of cases,
Work-RISQS estimates for specific race or Hispanic worker populations should be
used with caution.
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Definition: The nature of the most severe injury or illness as described
by the attending physician or other medical staff. If a medical diagnosis is missing
from the ED record, the chief complaint is commonly used for coding diagnosis.
For Work-RISQS queries, diagnosis is coded into one of 24 categories. Coding of
specific injury types may not always be uniform because of multiple diagnoses listed
in the ED record and ambiguities in terminology. For example, a worker may strain
or sprain their lower back while lifting an object. In one ED chart this may be
noted as a strained back and coded as strain or sprain whereas in another case the
chart may simply state "patient presented with back pain" resulting in
a diagnosis code of "other, n.e.c." To the extent possible these types
of issues have been minimized in the diagnosis data. Definitions of individual diagnoses
commonly follow standard medical practice. Anoxia, aspirated foreign object, ingested
foreign object, and poisoning have specific definitions to help distinguish particular
injuries.
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Anoxia is used when the patient cannot obtain sufficient oxygen, owing to
hampered breathing or lack of oxygen itself. For example, this category is used
when the diagnosis is strangulation, suffocation, asphyxia, or the patient has inhaled
combustion products such as carbon monoxide (CO), smoke, soot, etc.
Aspirated foreign object is used when an insoluble object causes choking
or is caught in the nose, lungs, or other parts of the airways and the object does
not lead to poisoning or anoxia.
Ingested foreign object is used when a patient swallowed an insoluble object
that is not likely to cause poisoning.
Poisoning is used when a patient swallowed liquid or soluble chemicals, drugs,
or medications including liquids such as bleach, fuel, or alcohol, and non-liquids
such as powdered detergents or cleaning products. Poisoning is also used when a
patient inhaled vapors, fumes, or gases (e.g., chemicals, cleaners, or fuels), except
when the vapors are carbon monoxide or other combustion products such as smoke.
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For Work-RISQS queries the 31 diagnosis categories used by NEISS-Work hospital abstracters
have been condensed to 24 categories. Categories with few cases such as diagnoses
of "Burn: electrical" and "Burn: not specified" have been combined
into a larger reportable group ("Burn: other"). Diagnoses of "Ingested
foreign object," "Aspirated foreign object," "Dental injury,"
"Hemorrhage," "Nerve damage," "Other," and "Submersion"
have been combined as "Other, n.e.c." (not elsewhere classified). The
diagnosis categories available for querying in Work-RISQS are:
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All (default)
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Burn: other
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Contusions, abrasions
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Foreign body
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Poisoning
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Amputation
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Burn: radiation
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Crushing
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Fracture
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Puncture
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Anoxia
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Burn: scald
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Dermatitis, conjunctivitis
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Hematoma
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Strain or sprain
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Avulsion
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Burn: thermal
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Dislocation
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Internal organ
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Other, n.e.c.
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Burn: chemical
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Concussions
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Electric shock
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Laceration
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Not stated
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Definition: The region or part of the body most seriously hurt.
The part of the body primarily or most severely affected by the injury or illness
is coded. However, the injured body part may overlap two coding categories such
as a laceration to a finger and palm where one coder may list the body part affected
as finger and another as hand. Similarly an injury to the eye may
be coded as eyeball or face depending upon the information and wording
provided in the ED chart. Caution should be used in interpreting Work-RISQS estimates
by body part when comparing to adjoining body parts or a specific part within a
larger body region. Selected injury types have coding rules to minimize this issue.
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Back injuries are coded as upper trunk when the injury is above the
waist or navel and lower trunk when below. A simple diagnosis of "back
injury" is coded as upper trunk.
Burn injuries involving less than 25% of the body are coded as the most severely
burned body part. More extensive burn injuries are coded as 25 to 50% of the body
or all parts of the body (i.e., more than 50% of the body).
Eye injuries are coded as eyeball when the injury occurred directly
to the eye itself, whereas injuries to the eyelids, eye brows, or the area immediately
around the eyes are coded as face injuries in the original hospital data
collection. However, NIOSH recodes eye and face injuries to conform to the
BLS Occupational Injury and Illness Classification System definition of
eye as the part of body affected. This definition classifies the sense organs of
sight located in the frontal portion of the head and is used for either one or both
eyes or when loss or impairment of sight is involved. In this definition the eye
includes: conjunctiva, cornea, eyeball, inside and outside of the eyelids, iris,
lacrimal glands, lens, optic nerve, orbit, retina, and upper and lower eyelashes.
Injuries to the eye brow area originally misclassified as eye injuries have been
recoded to face injuries.
Face injuries to primarily the eye area, as defined above, have been recoded
to eye injuries. Injuries to the facial area that were unspecified or more generally
involved a broader extent of the face are classified as face injuries although damage
to one or both eyes or mouth may have occurred.
Head injuries with general diagnoses of "head trauma," "closed
head injury," or "blunt head injury" and that do not have a specific
diagnosis such as laceration or concussion are coded as internal organ.
Anoxia, electric shock, poisoning, and submersion are coded as all
parts of the body.
Aspirated or ingested foreign object injuries are coded as internal
organ.
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The 26 individual part of body categories used by NEISS-Work hospital abstracters
are all available for use in Work-RISQS queries. The part of body categories are:
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All (default)
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Eye
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Internal
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Pubic Region
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25-50% of body
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Ankle
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Face
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Knee
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Shoulder
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All parts of body (>50%)
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Arm, lower
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Finger
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Leg, lower
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Toe
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Not stated
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Arm, upper
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Foot
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Leg, upper
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Trunk, lower
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Ear
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Hand
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Mouth
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Trunk, upper
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Elbow
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Head
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Neck
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Wrist
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Definition: The status of a patient after treatment in the ED categorized
as treated and released, treated and transferred/hospitalized, or unknown.
About half of treated and transferred/hospitalized patients are hospitalized in
the same facility as the ED. The other half are transferred to a different facility,
generally a specialty services hospital (e.g., a burn or pediatric hospital) or
other higher level care facility. Many of the transferred patients are hospitalized
in the new facility, but the final disposition is not always known.
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Definition: The manner in which the injury or illness was produced or inflicted
as coded in the BLS Occupational Injury and Illness Classification System (OIICS).
The OIICS coding manual is available online from the
BLS.
The event or exposure is classified in a hierarchical structure with general divisions:
- contact with objects
- falls
- bodily reaction and exertion
- exposure to harmful substances or environments
- transportation accidents
- fires and explosions
- assaults and violent acts
- other events or exposures
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Nonclassifiable
Each case is coded to the most significant level of detail permitted by using the
information abstracted from the ED record. Work-RISQS queries may be made to the
four-digit level (most detailed) for specific events or reported by all subgroups
by using the advance sort options. However, the more detailed levels may not produce
tables with reportable results because of the rarity of the event or lack of detail
in the ED record. For example, a worker who falls from a loading dock to the ground
below may be coded as 1123 Fall from loading dock if the ED record and the
abstractor provide that level of detail in the final NEISS-Work data. However, the
same injury might also be described in the ED chart as "fell at work."
In this instance, the event would be coded as 10 Fall, unspecified. This
same circumstance gives rise to injury estimates for specific events that may significantly
under estimate the true number because event details are never reported in the ED
record. Thus, estimates for individual events should be considered as minimum estimates.
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Definition: The object, substance, bodily motion, or exposure which directly
produced or inflicted the injury or illness as coded in the
BLS Occupational Injury and Illness Classification System.
The source is classified in a hierarchical structure with general divisions:
- Chemicals and chemical products
- Containers
- Furniture and fixtures
- Machinery
- Parts and materials
- Persons, plants, animals, and minerals
- Structures and surfaces
- Tools, instruments, and equipment
- Vehicles
- Other sources
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Nonclassifiable
The injury source is coded in a similar fashion and level of detail as the injury
event. However, there are far more codes available for source than event because
of the diversity of objects etc. that could produce an injury. For example, if a
worker were struck in the eye by a nail or brad, the source code would be 4212.
Other fasteners such as bolts, screws, and staples each have separate 4-digit source
codes. Estimates of specific sources should also be considered minimum estimates
as described for injury event estimates.
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Definition: The object, substance, or person that generated the source of
the injury or illness or that contributed to the event or exposure as coded in the
BLS Occupational Injury and Illness Classification System.
The secondary source is classified in a hierarchical structure with the same codes
as the source that inflicted the injury. An example of a secondary source would
be a hand tool that generated a flying object where the object struck a worker.
That is, if the worker noted above who was injured by a flying nail were hammering
at the time, the hammer would be the secondary source that generated or contributed
to the injury. Tools are common secondary sources, however, a secondary source is
not coded for every case because of a lack of injury event details or because there
simply was not a secondary source. About 80% of cases have no secondary source coded.
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National Injury/Illness Estimates: A Work-RISQS injury estimate query results
in a table of national injury and illness estimates where each table lists the query
parameters selected for this particular estimate and results. The table includes
a "National Estimate" in thousands, the percentage of the total estimated
injuries/illnesses for the year, and the confidence bounds expressed as a value
to be added to and subtracted from the national estimate to give the 95% confidence
interval.
National Injury/Illness Rates: A Work-RISQS injury rate query results in
a table of national injury and illness rate estimates where each table lists the
query parameters selected and results. The table includes a "National Estimate"
in thousands (i.e., the rate numerator and the same value that would be obtained
from the injury estimate report option), the worker population in full time equivalent
workers (i.e., the rate denominator), the injury/illness rate in incidents per 100
FTE during the time period, and the confidence bounds expressed as a value to be
added to and subtracted from the national rate to give the 95% confidence interval.
Data notes: Accompanying each query results table are data notes that pertain
to that specific query as well as several general notes.
Minimum reporting requirements:
Work-RISQS uses three criteria to determine if a national estimate is reportable.
First, estimates must be based on a minimum number of cases among the small sample
of U.S. hospitals within NEISS-Work. Second, the national estimate must exceed a
minimum number of injuries/illnesses. Third, the error associated with an estimate
must be small enough to indicate that the estimate would be reasonably reproducible
(i.e., the coefficient of variation is less than or equal to 33%). To be reportable
a national estimate must meet all three criteria. Work-RISQS automatically checks
that results meet the reporting requirements.
Disclaimer: Although NIOSH extends considerable
effort to insure reasonable data quality for Work-RISQS estimates, there are no
warranties expressed or implied with these data. The underlying data for queries
are subject to change without notice as errors, inconsistencies, or other data issues
arise. The objective of Work-RISQS is to provide public access to occupational injury
and illness data for use in workplace safety and injury prevention activities where
understanding the general magnitude of injuries, worker characteristics, and injury
events are important. Use of these data for other purposes should be done with caution.
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