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Comparing Industrial Hygiene and Environmental Approaches to Statistically Evaluating Indoor Air Data: Vapor Intrusion Applications
- 1. 1 Comparing Industrial Hygiene and Environmental Approaches to Statistically Evaluating Indoor Air Data: Vapor Intrusion Applications Chris Lutes CH2M, Raleigh, NC John Lowe, CIH CH2M, Spokane, WA Dr. Loren Lund CH2M, Shelley, ID A&WMA’s 110th Annual Conference and Exposition Pittsburgh, Pennsylvania June 5-8, 2017
- 2. 2 Introduction • Workers in vapor intrusion (VI)-impacted buildings can fall under both occupational and environmental cleanup regulatory requirements. • Therefore, there can be multiple limits for assessing potential VI exposures: – Risk-based screening levels such as Vapor Intrusion Screening Levels (VISLs). – Occupational Exposure Limits (OELs) such as Permissible Exposure Limits (PELs) or Threshold Limit Values (TLVs) – which are ACGIH guidelines • There can be a large disparity between VISLs and OELs for some chemicals. • This can lead to confusing situations in risk management and risk communication.
- 3. 3 WHAT IS VAPOR INTRUSION (VI)? “… migration of hazardous vapors from the subsurface into … overlying buildings” USEPA (2015)
- 4. 44 VI Regulatory Drivers/Policies (TCE Example) EPA R9 CalEPA HDOH EPA R10 AK DEC NJDEP MADEP NHDES CT DPH/DEEPOhio EPA IDEM EPA R6 EPA R3 EPA R4 Values applied throughout the U.S. EPA R7 EPA Region 7 (Nov, 2016): “The action level for an industrial/commercial scenario…..is 6 µg/m3. An exceedance of the TCE action level indicates a potential imminent threat…. Region 7 should expedite early or interim actions….as quickly as possible…immediate site actions could include relocation, restricting the time….workers remain”
- 5. 55 The Problem in a Nutshell Same molecule but different standards of protection depending on how exposure occurs. Exposure is managed as part of environment al cleanup. EPA has primacy. Exposure is managed as a matter of occupational health. OSHA has primacy.
- 6. 6 Objectives • Compare VISLs and OELs (in this case, TLVs) with several topics: what kinds of populations are protected; how are carcinogens assessed, as examples. – Describe some differences in methods and ‘philosophies’ about controlling toxic exposures used by different authorities. • Compare the respective risk management frameworks for using VISLs and OELs in decision-making and taking actions to control exposures to VOCs in indoor air. – Examples are presented for selected volatile organic compounds (VOCs) which have been detected in indoor air at VI sites.
- 7. 77 How are carcinogenic substances addressed? Topic Environmental (VISL) Occupational (TLV) How are cancer risk- based levels developed? Extrapolated using modeling from high- dose animal studies or highly-exposed groups of humans. Qualtitative - based on weight-of- evidence (WOE) for human cancer. What level of protection is achieved? 10 -6 to 10 -4 risk range; cost and technical feasibility not considered. Follows "ALARA" approach. Other OELs have used 10 -3 risk. Cost and technical feasibility considered
- 8. 88 How are non-carcinogenic substances addressed? Topic VISL TLV How are non-cancer risk-based levels developed? Extrapolated from NOAEL, LOAEL or BMD from animal studies or exposed human groups using modeling. Based on studies identifying minimal and no-adverse effect levels. Emphasis on inhalation exposures ideally from human experience. What populations are protected? All individuals including sensitive subpopulations. "Nearly all workers" (adults and older teens). May not protect sensitive individuals.
- 10. 1010 Occupational Risk Management Approaches
- 11. 1111 Screening Levels (SLs) and TLVs for Selected VOCs Found at VI Sites Analyte Carcinogenic SL TR=1 x 10-6 (ug/m3 ) Carcinogenic SL TR=1 x 10-4 (ug/m3 ) Non- carcinogenic SL THQ=1 (µg/m3 ) Non- carcinogenic SL THQ=3 (µg/m3 ) TLV-TWA (ug/m3 ) Benzene 1.6 160 130 390 1,600 Trichloroethylene 3 300 8.8 26.4 54,000 Notes: SL = screening level. TR = target cancer risk. THQ = target hazard quotient TLV-TWA = Threshold Limit Value based on 8-hour Time-Weighted Average. The non-carcinogenic VISL, based on a THQ of 1. The carcinogenic VISL, based on a 1 x 10-6 cancer risk, is shown along with the target risk range (EPA, 1991).
- 12. 1212 Benzene
- 14. 14 Harmonizing Risk Management Frameworks • EPA has a growing role in managing chemical exposures to workers: – VI in commercial/industrial buildings next to or overlying hazardous waste sites. – TSCA rules under the reauthorization act (Lautenberg Act of 2016) specifically defines workers as a “susceptible subpopulation” • Challenges to the occupational health community: – There will be disparities between limits for assessing occupational and environmental exposures, for many chemicals – The disparities in the numbers won’t be resolved soon – Harmonize the risk management frameworks: • Reduce operational disruptions (evacuations of VI-impacted buildings) and risk communication problems.
- 15. 15 One Concept for Harmonization: Ranking VI Workplace Risks a/ • Universe of Workplace Hazards – Examples: Physical, chemical, biological, ergonomic, psychosocial, mechanical, electrical. a/ Using the ANSI Z-10 Occupational Health and Safety Management System Potential Hazard Present? (Y, N, ?) Description of Hazard Possible Effects Timeframe (acute/chronic) Risk Code (RAC) Physical Noise Trips/slips Chemical Particulates Indoor Vapors VI Vapors Biological Mold/mildew Ergonomic
- 16. 16 Another Concept for Harmonizing Environmental and Occupational Risk Management Frameworks Description HHSC Code A Likely to occur immediately B Probably will occur in time C Possible to occur in time D Unlikely to occur Death, permanent total disability, or loss of facility or asset I 1 Critical 1 Critical 2 Serious 4 Minor Permanent partial disability or major property damage II 1 Critical 2 Serious 3 Moderate 4 Minor Lost workday injury or compensable injury, or minor property damage III 2 Serious 3 Moderate 4 Minor 5 Negligible Injury involving first aid or minor supportive medical treatment, a minimal threat to personnel or property, or a violation of a standard IV 4 Minor 4 Minor 5 Negligible 5 Negligible Hazard Severity Mishap Probability
- 17. 17 Conclusions • There is a distinct difference numerically between OELs (in this case, TLVs) and VISLs. • However, these differences become more understandable in the context of how these values are used: – TLVs –based largely on threshold for adverse effects but used in a more precautionary way. – VISLs - levels with larger margins of safety that are used in a risk management framework with some limited flexibility. • Neither set of values should be used without careful consideration of the assumptions and limitations associated with them.
- 18. 18 Conclusions (continued) • Harmonization will remain difficult for some chemicals (TCE) until values are revised. • There are example of some chemicals where the basis exists for harmonizing environmental and occupational activities (benzene). • Efforts to harmonize environmental and occupational levels are under way but may occur over many years. • Other risk assessment methods might be used to help bridge the gap between environmental and occupational practice. – American National Standards Institute (ANSI) Z-10 standard, which has been incorporated into DoD guidelines.
- 21. 21 Issues with Exposure Limits for VI in Workplaces • VI is addressed as a cleanup matter – Managed in accordance with EPA/State guidelines under CERCLA/RCRA • EPA’s guidance rejects use of OELs in assessing exposures from VI in spaces containing workplaces – EPA prefers the values (VISLs, RMLs) – there are examples of sites where this has been a disruption to facility operations • Current regulatory practice defaults to the VISLs (and RMLs). • Conflicting jurisdiction with Federal agencies (EPA v OSHA). • Multiple authorities potentially have a role in VI
Editor's Notes
- There are a number of different OELs, such as OSHA Permissible Exposure Limits (PELs), NIOSH Recommended Exposure Limits (RELs) and ACGIH Threshold Limit Values (TLVs). We won’t explore the differences between these values in this presentation. We focus on TLVs for comparison with VISLs, because TLVs are used world-wide, and are updated more frequently than PELs or RELs.
- Comparison of occupational exposure limits (PEL, TLV) and another short-term exposure limit (the AEGL-1) with screening levels for VI, used for TCE. The TCE screening levels cover a range of values for both chronic and short-term exposures. This shows how VI screening levels are somewhat of a patchwork
- This is an example of how EPA has a very quantitative approach to VISL development: the methods for assessing cancer risks and developing numerical unit risk factors. In contrast, TLVs for carcinogenic substances are more qualitative and based on WOE, However, for chemicals identified as known or probable human carcinogens, ACGIH recommends reducing exposures to as low as feasible. There are a few examples of OELs that are based on lifetime cancer risk – these are recent OSHA Permissible Exposure Limits (PELs) for substances such as dichloromethane. The 10-3 risk used by OSHA is based on the reasoning that 10-3 risk is also the fatality risk of accidents in typical industrial facilities. The purpose for using the 10-3 target risk is to avoid diverting limited health and safety resources from larger hazards to controlling small cancer risks.
- This is another example of EPA’s more quantitative approach for developing toxicity values. This also shows the differences in populations that are protected – EPA’s definition of the RfC specifically includes sensitive populations, “An inhalation reference concentration (RfC) is defined as an estimate (with an uncertainty spanning perhaps an order of magnitude) of a continuous inhalation exposure to the human population (including sensitive subgroups) that is likely to be without appreciable risk BMD = benchmark dose
- Example of where environmental and occupational risk management ranges overlap: in the range between 160 and 390 ug/m3, both a RPM and an industrial hygienist would recognize the need to reduce exposures, though they may use different sets of tools to achieve that objective. The overlap in these levels makes it easier for RPMs and IHs to coordinate efforts in managing VI exposures in commercial/industrial buildings. Benzene represents an example where there is some existing harmonization of the levels used to assess both environmental and occupational risks.
- In contrast, TCE is an example where as yet there is no harmonization. IHs may conclude no significant exposures are occurring (1% of the TLV is a concentration of 540 ug/m3 in air), which would be a level of substantial concern to a RPM. This risks disruption of building operations, and risk communication problems (for example, the IH indicates “all clear”, and the RPM is requiring building occupants to be evacuated.
- The disparities in occupational and environmental limits are slowly being resolved – primarily by movement in the IH community. A series of paper was published in November 2015 in the Journal of Occupational and Environmental Health – which includes more of a movement to EPA-style exposure levels. See also: http://www.safetyandhealthmagazine.com/articles/14642-tsca-reform-what-does-it-mean-for-worker-safety
- This matrix is part of the ANSI Z-10 OSHMS standard, for identifying and ranking workplace hazards – the objective is to place exposures from VI in context with the range of occupational risks, which must be prioritized in order to allocate resources for effectively controlling risks. Physical: Noise; Vibration; Heat/Cold; Radiation- Ionizing, Non-ionizing, Infrared, UV, Visible Chemical: Particulate – Dust, Mist, Fume, Fibers; Liquids - Acid/Bases, Solvents; Vapors and gases Biological: Animal/Insect Pests; Microbial – Bacteria, Viruses, Mold/Mildew Ergonomic: Repetitive motion injuries; Poor workplace design; Poor equipment design; Unusual work schedules
- A concept for harmonization: the CERCLA risk ranges (lifetime cancer risks, non-cancer Hazard Quotients) overlain on a risk assessment matrix published in the ANSI Z-10 standard “Occupational Health and Safety Management Systems”. This is a hypothetical concept, and further discussions
- “Current practice” – current compliance practices for VI sites involves defaulting to the VISLs and RMLs for assessing workplaces. VISLs – Vapor Intrusion Screening Levels (VISLs) and Removal Management Levels (RMLs). Where “this has been a problem” comes in: TCE detected in indoor air from VI triggering building evacuation, because of the developmental toxic hazard with subacute exposures. The conflicting jurisdiction: Need to read Laurence Kirsch’s paper, but the short story from him is that EPA usurps OSHA’s authority to determine workplace exposure standards. The issues about standards of protectiveness and age of the standards (OSHA’s) arise – as yet OSHA hasn’t engaged (something about silica). Multiple directorates/authorities – Multiple directorates in DoD have a responsibility for protection of human health (similar to the OSHA and EPA issue) – however, there are differences in approaches, in certain ways – VISLs and TLVs are one example.