Introduction to Exposure Assessment Strategies and Statistics (Part 1 Basic Overview)

Exposure Assessment Strategies Committee

Efficient and Effective IH Programs

• A well-rationalized IH program relies on a

thorough understanding of what is known, and

what is not known

• The better the industrial hygienist understands

exposures, the better he or she is able to direct

and prioritize the IH program

2

CONCEPTS FROM (AKA AIHA SAMPLING STRATEGY MANUAL)

Exposure Assessment

• The process of defining exposure profiles and

judging the acceptability of workplace

exposures to environmental agents

4

Professional Judgment

• Vital for identifying similar exposure groups

• Necessary for designing sampling strategies

• Essential for judging exposures

• Important for choosing health hazard control strategies

…..but what is “Professional Judgment?”

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Why is Exposure Assessment

Important?• Growing number of real and perceived risks that

industrial hygiene programs must be prepared to manage

• Programs in the past were less rigorous, now they must be thorough, systematic, well-documented and efficient

Is required by 10 CFR 851, Worker Safety and Health Program, (ref. 851.21, Hazard identification and assessmentand Appendix A6, Industrial Hygiene

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Exposure Assessments

• Exposure Assessments are used to:

– Understand, prioritize, and manage

exposures

– Identify exposures that need better

characterization, or careful routine

tracking

– Focus worker training programs

– Target medical surveillance programs

– Define PPE requirements

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Exposure Assessment

• Exposure Assessment is a judgment (3

categories):

– Acceptable health risk

– Unacceptable health risk

– Uncertain health risk

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Comprehensive Strategy

• Comprehensive strategy: directed at

assessing all exposures for all workers on all

days

• Why? Exposures occur whether we are

there or not!

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EXPOSURE ASSESSMENT STRATEGIES

1. Start2. Basic Characterization3. Exposure Assessment4. Further Information Gathering5. Health Hazard Control 6. Reassessment7. Communications and Documentation

Reminder baseline, surveys, and periodic resurveys and/or exposure monitoring is required "as appropriate" by 10 CFR 851 - Appendix A6

Start

Basic

Characterization (BC)

Exposure

Risk

Assessment

(ERA)

Exposure

Management & Controls

(EMC)

Qualitative

Assessment

Sampling &

Quantitative

Assessment

Applying Correct

Level Of Response

SIMPLIFIED EXPOSURE STRATEGY FLOW

1. Set Decision Criteria

2. Document Qualitative Exposure Judgment

3. Gather Samples Of Exposures

4. Statistical Analysis Of Sampling Data (Quantitative Exposure Judgment)

5. Identify Needed Controls

6. Compare Qualitative And Quantitative to Calibrate/Continuously Improve Judgments.

Basic Characterization

The Qualitative Assessment

We Are Here

EXPOSURE DECISION CRITERIA

• Decision Statistic

Decided early in process

Match up with organization’s risk tolerance

Needed confidence in decisions

95th percentile compared to OEL?

UTL 95%, 95%

Higher confidence higher cost, sometimes unattainable

• Occupational Exposure Limits (OEL)

HOW DO I NEED TO ARRANGE ASSESSMENTS?

SIMILAR EXPOSURE GROUP (SEG)• Why Use SEG?

• HR Job Title?

• Comparable job tasks

• Agents in work environment

• Work habits

• Machinery

• Engineering controls

• Administrative factors

• Same geographical area?

•Data Driven!!!!!

WHAT DATA DO I NEED TO COLLECT?

DATA TO COLLECT FOR BASIC CHARACTERIZATION

• Who, What, Where, When, Why, How

• Who are the employees covered by this assessment

• What job/task/SEG was assessed

• What frequency is the job/task done

• What were weather/environmental conditions

• Where was the job/task located

• Where was equipment

• When: date/time of your assessment

DATA TO COLLECT FOR BASIC CHARACTERIZATION

• Why is the assessment valid/representative of the job/task

• Who, What, Where, When, Why, How regarding Controls and PPE in use

• Document your judgment of the exposure.

AIHA Exposure Category 0-4 Initial Rating & 1-3 Certainty Level

Or 5 by 5 table ranking

Document why/how you reached your judgment

AIHA Categories For Grouping and Prioritization

SEG Exposure Control

Category**

0 (<1% of OEL)

1 (<10% of OEL)

2 (10-50% of OEL)

3 (50-100% of OEL)

4+ (>100% of OEL,

Multiples of OEL; e.g.,

based on respirator APFs)

Your decision is made on where you think the exposure’s 95th

percentile as % of the OEL falls

Exposure Risk Assessment

Sampling & Quantitative Assessment

We Are Here

DATA TO COLLECT FOR SAMPLING & QUANTITATIVE ASSESSMENT

• What type of sample (Personal, Area)

• Was it valid/representative of the job/task

• Was the sample conducted correctly

• What was the job/task

• Where was the job/task

• Date/time of sample

• Length of sample

• Length of shift

• Who was sampled

• Employee activity during sample

• Frequency of job/task

• IH Equipment used

• Weather/Environmental Conditions

• PPE in use

• Document your judgment of the exposure.

AIHA Exposure Category 0-4 Initial Rating & 1-3 Certainty Level

RESULTS FROM INDUSTRIAL HYGIENE SAMPLES

• Results of lab analysis

• What type of analysis was done

• Was it lab void

• Limit of detection

• Was the lab accredited

• Date/time sample sent to lab

• Date/time sample received from lab

How do you plan on getting results into the data management system?

Exposure Management & Controls

Applying Correct Level Of Response

Start

Basic

Characterization

Exposure

Risk

Assessment

Exposure Management & Controls

AIHA’s Systematic

Categorization &

Controls Model

Exposure Management & Control Categories

** - Note: Decisions are made on the exposure’s percentile compared to the OEL at a level that fits the organization’s risk

tolerance level. Decision statistic = 90th, 95th, 99th percentile.

SEG Exposure Control

Category**

Applicable Management/ Controls

0 (<1% of OEL) no action

1 (<10% of OEL) procedures and training,

general hazard communication

2 (10-50% of OEL) + chemical specific hazard communication,

periodic exposure monitoring,

3 (50-100% of OEL) + required exposure monitoring,

workplace inspections to verify work practice controls,

medical surveillance,

biological monitoring,

4+ (>100% of OEL,

Multiples of OEL; e.g.,

based on respirator APFs)

+ implement hierarchy of controls,

monitoring to validate respirator protection factor selection,

% OEL

• Exposure/OEL * 100 = %OEL

• Example 35/100 *100 = 35% OEL

• Can be used to simplify analysis

• Helps normalize data (noise, extended shift)

• Example: Ethyl Bromide

• Using ACGIH TLV 5 PPM as OEL

• Results 1.23 PPM TWA? or

• 24.6 % OEL (Easy to convey results)

Geometric Standard Deviation (GSD)

• GSD helps identify variability in data

• Basic tool to measure if data is similar

• Rule of thumb GSD of 2.5 or greater is overly variable

Systems Approach Towards Improving Judgments & Calibrating The Industrial Hygienist

IH Exposure Judgment Biases• Research shows exposure judgments of IH’s are inaccurate when

statistical tools are not used!

– Judgments biased lower than actual exposure

That means under-protection for workers!

– This fact is Worse when comparison to X95th is used

Welcome to the Dart Throwing Monkey ≥ IH concept

IH EXPOSURE JUDGMENT

• Statistical tools make exposure judgments better

• Use of rules of thumb increase accuracy and decrease bias

• Documenting decision rationale, yields better judgment

• Move from under estimating exposure judgments towards judging the true exposure

Thank You!

Thank you for your time

Questions

End Of Meeting 1 (Basic Overview)

Homework: Use some of your unsampled tasks to

create a Basic Characterization.

Try to create an Exposure Risk Assessment using

your sampling data.

Try using AIHA Categories