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EHS 655
Lecture 2:
Introduction and overview,
continued
Setting the stage

So, what exposure will we be focusing on this
semester?
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Exposure selected based on…
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Ubiquity of exposure (e.g., many sources)
Variability of exposure
Range of health effects
Availability of dataset
Over-emphasis on chemicals at SPH
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Setting the stage
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Will use dataset of noise exposures and two health
outcomes related to noise
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Hearing loss
Hypertension
Concepts from this analysis can be readily
applied to
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Any hazard
Workplace and community
exposures
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Noise and associated health effects
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Noise among most common occupational exposures
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Noise-induced hearing loss (NIHL) among most
common, well-understood occupational diseases
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100% preventable, but permanent, irreversible
Profound social and occupational effects
Linked to injuries and non-auditory effects
Time course of NIHL from variable noise unclear
Non-auditory effects of noise less well-understood
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Hypertension, ischemic heart disease, etc
NIOSH, 1998; Berger, Royster, Royster, Driscoll, Layne, 2000
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Noise and hearing loss
Henderson D et al, Ear Hear 2006
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Noise and hearing loss
Henderson D et al, Ear Hear 2006
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Noise and hearing loss
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Noise and hearing loss
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Noise and CVD
Van Kempen et al, Environ Health Persp, 2002
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Environmental noise and CVD
Meta-analysis, 7-17% increase in CVD per 10 dB increase
Basner et al, Lancet, 2014
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Environmental
noise and CVD
World Health Organization: >1
million healthy life years (i.e.,
Disability-Adjusted Life Years,
DALYs) lost annually due to
environmental noise
(Note: does not consider
occupational noise)
Basner et al, Lancet, 2014
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Environmental noise and CVD
Estimated US
CVD savings
from 5 dB
reduction in
population
noise in 2014:
$3.9 billion
Swinburn et al, Am J Prev Med, 2015
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Occup.
noise and
CVD
Retrospective cohort, 27,464 workers, mean 92 dBA, 24 years avg f/u
Davies et al, Epidemiol, 2005
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One way to assess CVD: blood pressure
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Measured using 2 numbers (e.g., 120 over 80 or 120/80)
First number = systolic blood pressure
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Measures the pressure in blood vessels when heart beats
Second number = diastolic blood pressure
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Measures pressure in blood vessels when heart rests between
beats
https://www.cdc.gov/bloodpressure/measure.htm
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Okay, so noise is bad. Why do we
need another study?

Anyone know Hill’s Criteria for Causality?
http://nfs.unipv.it/nfs/minf/dispense/patgen/lectures/files/disease_causality.html
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NIHL claims in one industry with highly
variable noise
7.5% 6000
workforce 1984-96, 21% accepted NIHL claims
Number of claims
5000
4000
1998 cost: $57 mil
All other
industries
All Industries
3000
Construction
2000
1000
0
84 85 86 87 88 89 90 91 92 93 94 95 96 97 98
Year claim was filed (1984-1998)
Daniell, Fulton-Kehoe, Cohen, Swan, Franklin, 2002
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Overview of study (some of) our data
come from
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Prospective study of early NIHL among construction
workers, 2000-2010
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Why are studies like this rare?
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Workers recruited at start of apprenticeship programs
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Annual subject visit to University of Washington,
Seattle with:
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Extensive battery of hearing tests
Survey of work experience, tasks, perceptions of exposure
Direct exposure measurements on cohort infeasible
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Blood pressure data from study
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Did not actually collect blood pressure data
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I have simulated data and added it to dataset provided
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Everything else in the dataset is real
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Data needed to understand risk of
health effects of noise
Frequency
Protective
behaviors
Duration
Dose
Personal
risk factors
Intensity
Variability
Frequency x Duration x Intensity
= Exposure
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Exposure assessment in construction
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Exposure assessment
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Full-shift dosimetry measurements
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Dosimeters datalog exposure
parameters at 1-min intervals
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Convenience sample of construction workers at sites around
Puget Sound
Shifts not all exactly 8 hours
Average level (LEQ)
Maximum level (LMAX)
Workers simultaneously record
tasks, hearing protector use, etc.
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Task-based exposure assessment
100.0
Task A
Task B
Task A
Task C
Task A
Noise Level (dBA)
90.0
80.0
70.0
60.0
Measured
Exposure
50.0
40.0
0
50
100
150
200
250
Time (Minutes)
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Subjective rating (SR) of noise
exposure
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Workers assess own noise exposure via SR
What percent of time were
you exposed to each of the
following noise levels at
work?
_____% No louder than a normal speaking voice
_____% As loud as a vacuum
_____% As loud as a gas lawnmower
_____% As loud as a chainsaw
The total should add to
about 100 percent.
_____% As loud or louder than a siren
Total = about 100%
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Simultaneously measure noise exposure
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Combine for quantitative exposure estimate
Neitzel, Daniell, Sheppard, Davies, Seixas, 2009
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Data needed to understand risk of
health effects of noise
Frequency
Protective
behaviors
Duration
Dose
Personal
risk factors
Intensity
Variability
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Variability – alternative metrics
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Different exposure parameters may help explain
health effects
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Average
Maximum or peak
Can also compute ratios of these parameters
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Maximum/average (peakiness of levels)
Seixas, Sheppard, Neitzel, 2005; Rappaport, 1991
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Data needed to understand risk of
health effects of noise
Frequency
Protective
behaviors
Duration
Dose
Personal
risk factors
Intensity
Variability
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Non-occupational sources of noise in
life
Others?
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Data needed to understand risk of
health effects of noise
Frequency
Protective
behaviors
Duration
Dose
Personal
risk factors
Intensity
Variability
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Factors to consider regarding use of
hearing protectors
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Is it used and is it effective?
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Other protective “behaviors”
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Acoustic reflex
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Biomarker of exposure
and susceptibility
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Temporary Threshold
Shift at 2 mins postexposure, TTS2
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Data needed to understand risk of
health effects of noise
Frequency
Protective
behaviors
Duration
Dose
Personal
risk factors
Intensity
Variability
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From the reading
Kauppinen 1991, Appl Occup Environ Hyg
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Introduction to the data files
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Types of files
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Dataset files
Variable description files
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You’ll be using and referring to both regularly
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How they’ll be introduced
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New version of dataset most weeks, with additional variables
and (at least once) more measurements
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Introduction to Stata
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The program
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The do-file
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Why use a do-file?
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Ease of manipulation of data
Documentation of manipulations and analyses
Preserve original data file
I’m forcing you to
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Resources
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Statistics Consulting Group, University of CaliforniaLos Angeles Institute for Digital Research and
Education
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Which statistical analysis should I use?
http://www.ats.ucla.edu/stat/mult_pkg/whatstat/
Stata online help files
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Frequently asked questions on using Stata
http://www.stata.com/support/faqs/
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