Anthony “Tony” Havics, PE, CIH – Occupational Exposure Limits and Their Relationship to Limits for the General Public

Air Date: 1-12-2018|Episode 490

This week on IAQ Radio we welcome Anthony “Tony” Havics to talk about how occupational exposure limits are related to limits for the general public. This is a topic that causes a lot of confusion and at times misinformation. Can we use OEL’s or should we avoid them altogether?


Full Description:

This week on IAQ Radio we welcome Anthony “Tony” Havics to talk about how occupational exposure limits are related to limits for the general public. This is a topic that causes a lot of confusion and at times misinformation. Can we use OEL’s or should we avoid them altogether?

Mr. Havics is an Honors graduate from Georgia Institute of Technology with a Bachelor’s Degree in Mechanical Engineering and is a registered Professional Environmental Engineer (PE) with over 25 years of experience. He has provided front end investigation, development of plans & specifications, development of work plans, cost estimation, and oversight of numerous facilities for remediation, refurbishing, or decommissioning including a launch pad, dam gates, a baseball stadium, a tire factory with 59 buildings, a biologically contaminated L1011, a hospital, JP-6 fuel tanks, former mental institute, former military buildings, etc. In the field of microscopy, he has performed analysis for asbestos, contaminants in products, other minerals, fibers, fungi, engineering properties, and has testified in federal court as an expert microscopist. Andrew has also performed failure analysis and forensic testing on numerous building products such as roofs, windows, flooring, drywall, piping, etc.

Z-Man’s Blog:

“17 Out of a Million”

Tony Havics, PE, CIH was our guest on today’s episode of IAQradio. For 30+ years he has provided front end investigation, development of plans and specs, cost estimated and provided oversight on a wide range of facilities including remediation, refurbishment and decommissioning. He has performed forensic testing and failure analysis of building products and has testified in federal court as an expert microscopist.

Nuggets mined from today’s episode:

What is exposure? Combining an exposed population to an exposure scenario and what we are trying to prevent.

Is the exposure once per day or 250 workdays per year or 350 days for the general population? Exposure scenario limits can be based upon acute effects 10-30 minutes, 8 hour work day, or 24 continuous hours for the general public. Moderate exposures of 1 month-3 years. Is the exposure frequency over an 8 hour work period or lifetime of work?

The exposure concentration: the location, the situation and the exposure pattern below which you don’t expect disease.

The majority of exposures are airborne exposures. There are some ingestion exposures.

Exposure- who are you protecting, look at multiple scenarios and chose a conservative one. Concentration X Time = Dose= Exposure Limit.

Is it 5 days of 8 hour exposures with 16 hours recovery time between. Or is it on a spacecraft or submarine where there is no recovery period. Is the effect of critical importance? How to play it, using either risk or threshold type approach.

Is the chemical exposure below where it poses a problem or is it a carcinogen where every molecule brings risk. Cancer is death. Odor is nuisance and is reversible. Cancer creates fear in the general population and drives down exposure numbers. What organs are affected? kidneys, liver, heart, blood, etc. An uncertainty factor goes into the numbers. 3-300, 10-30 occupational. 30-3000 general population. Genotoxic direct genetic risk in cancer versus indirect effect. Nongenotoxic cancer- threshold below where risk doesn’t increase.

Furan has the lowest feasible exposure limit. Furan is the result of incomplete combustion. [TCDF 2,3,7,8-tetrachlorodibenzofuran (TCDF) TCDD 2,3,7,8-Tetrachlorodibenzo-p-dioxin which is often referred to simply as dioxin].

Control Banding is used to group risks and set point value ranges. Carcinogens are the most tightly controlled.

Carcinogens drop exposure to low values. Carcinogens take 10-50 years to develop disease. Professionals doing an investigation should look at other effects- such as what to use for a warning sign- such as color loss in eye vision to help catch exposure early on.

Cost benefit relationship. We live in a world reliant upon the many benefits of petrochemicals so we accept exposure to benzene and toluene. We rely upon pharmaceuticals and accept the side effects and risks.

Acceptable Occupational Exposure was decided by the U.S. Supreme Court in 1980 to be 1 person in 10,000. The EPA Clean Air Act won’t look at anything under 1 in 1,000,000. The state of California regulates risk for consumers as 1 in 100,000.

Sensitization is response to a high dose of a chemical in which the body’s immune system acts. The peak dose creates the sensitization. Additional exposure causes greater reaction. Sensitization is not disease. Reaction is disease. In occupational exposure sensitized workers can be removed from the workplace. In non-occupational exposure a residential occupant is reacting to something within their home, removal from home isn’t a viable option. Sensitization can take months to years to occur.

Chemicals such as Bacillus subtilis, maleic anhydride and isocyanates are known to trigger asthma and sensitization. The exposure risk factor number does not prevent sensitization.  Bacillus subtilis is commonly found in cleaning and deodorizing products.

Comparison of Exposure Limits.

American Conference of Governmental Industrial Hygienists (ACGIH). Threshold Limit Value (TLV): 0.00006 mg/m3 Ceiling (Listed under Subtilisins, as crystalline active enzyme).

National Institute for Occupational Safety and Health (NIOSH). Recommended Exposure Limit (REL): 0.00006 mg/m3 STEL (60 Minutes).

Lead Exposure Limits.  The NIOSH Recommended Exposure Limit (REL) for lead is a Time Weighted Average of 50 micrograms per cubic meter of air (µg/m3) over 8-hours. The required (OSHA) Permissible Exposure Limit (PEL) for lead is also no greater than 50 µg/m3 averaged over an 8-hour period.

Workplace Standards. OSHA has established workplace levels to protect the health of people occupationally exposed to cadmium. Permissible Exposure Limit- TWA (PEL): 5 µg/m3 (fumes).

Control banding- low exposure limit. One person’s chocolate allergy doesn’t mean chocolate should be banned. Setting mold exposure limits is tricky because other substances are also present (dust mites, protozoa, etc.). Exposure limits can be established for formaldehyde and glutaraldehyde.

Definitions for Exposure Limits

Permissible Exposure Limit (PEL) [OSHA] An employee’s exposure to any substance…shall not exceed the 8hour TWA given for that substance for any 8‐hour work shift of a 40‐hour work week.

Threshold Limit Value (TLV) [ACGIH]  TLVs refer to airborne concentrations of chemicals substances and represent conditions under which it is believed that nearly all workers may be repeatedly exposed, day after day, over a working lifetime without adverse effects.

Workplace Environmental Exposure Level (WEEL) [AIHA/TERA]  – See TLV

Recommended Exposure level (REL) [NIOSH]  Occupational exposure limits recommended by NIOSH as protective of worker health and safety over a working lifetime. This limit is frequently expressed as a time‐weighted average (TWA) exposure for up to 10 hr/day during a 40‐hr workweek.

Minimum Risk Level (MRL) [ATSDR] Estimate of the daily human exposure to a hazardous substance that is likely to be without appreciable risk of adverse non-cancer health effects over a specific duration of exposure.

Acute 1‐14 days), intermediate (>14‐364 days), and chronic (>365 days)

Slope Factor (SF) Upper bound (95% CL) on the increased cancer risk from a lifetime oral exposure to an agent.

Risk Based Target Level  Numeric values that are protective of human health, safety; based upon acceptable an acceptable risk.

RfD  Estimate of a daily oral exposure to the human population  (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime.

RfC  Estimate of a continuous inhalation exposure to the human  population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime.

Hazard Quotient Ratio of the level of exposure of a chemical of concern over a specified time period to a RfD (or RfC) for that chemical(s) of concern derived for a similar exposure period. One day of exposure is different than 100s of days of exposure. Exposure to 1 PPM of a substance allowable at 10 PPM can trigger panic so an added safety factor is built in. Nuisance value can irritate.

Ambient Air Quality Limit [AAQL]. Primary standards provide public health protection, including protecting the health of “sensitive” populations such as asthmatics, children, and the elderly. Community exposure limits (using a RAGS approach, Risk Assessment Guidelines) were established in the late 1960s and 1970s. What’s acceptable downwind and what’s acceptable at the fence line around the facility.

Secondary standards provide public welfare protection, including protection against decreased visibility and damage to animals, crops, vegetation, and buildings.

8‐Hour Time Weighted Average (TWA)  An average exposure over an 8hr workday weighted by time of exposure  Short Term Exposure Limit (STEL).

A STEL is defined as a 15minute TWA exposure which should not be exceeded any time during the workday.

Added Comments:

OSHA PEL while required may not be the deciding factor on disease or not disease.

Higher risks are acceptable for industrial sites than for residential sites. The general population contains the young, elderly, asthmatics, etc.

Exposure guidelines for non-occupational exposure reduce morbidity, disease, improve enjoyment of life, breathe well not smell something.

Time period/frequency/adverse effect. Odor is the driver for nuisance effect versus an increase in heart attacks over lifetime. Longer exposure periods and shorter recovery periods.

Rat and mouse study data cannot be trusted. Rats and mice can slow down their inhalation during testing. Rats will wet the fur on paws and breathe through it using it as a respirator. Some rat and mouse strains are bred to be super sensitive.  Rat and mouse studies may include safety factors of 3-10 fold.

The ASHRAE Indoor Air Quality Standard recommendation of using 1/10th or 1/100th of the TLV when no national limit exists ignores the method by which the TLV was developed. When you know where the sources from which limit comes from it may help in developing something useful. Using 3X or 10X the TLV for some chemicals for sensitive or variable populations may be applicable in specific situations. Cheat and go to REACH in Europe which uses default exposure limits, more general population related than occupational realm.

The OSHA PEL for formaldehyde is based on cancer. The TLV is lower and is based on irritation and nuisance, the value of the irritant (where 20% of people will be irritated). In the non-occupational world I would look at less than 5% response or look at the data and take the TLV reduced  6X lower. Is it reversible? Is it causing annoyance and lowering productivity. As a preventative measure its more cost effective to control one workspace rather than make changes that affect everyone else.

In California studies of pregnant women who were legally taking amphetamines for weight loss were used to set standards in clandestine meth lab cleanups.

Final Comments:

17 out a 1,000,000 is the chances of being struck by lightning.

What is the acceptable level of risk?

Does it make sense?

Z-Man’s Final Comments

Tony is a native Pittsburgher, did the interview in my office studio. It was a great pleasure spending most of the day with him. He is extremely knowledgeable and accomplished and was generous with his time allowing me to pick his brain.

Z-Man signing off

Trivia Question:

What agency established “NCEL” the nickel exposure limit?

Trivia Answer:


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