TLV® Physical Agents Introduction

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Policy Statement on the Uses of TLVs® and BEIs®

The Threshold Limit Values (TLVs®) and Biological Exposure Indices (BEIs®) are developed as guidelines to assist in the control of health hazards. These recommendations or guidelines are intended for use in the practice of industrial hygiene, to be interpreted and applied only by a person trained in this discipline. They are not developed for use as legal standards and ACGIH® does not advocate their use as such. However, it is recognized that in certain circumstances individuals or organizations may wish to make use of these recommendations or guidelines as a supplement to their occupational safety and health program. ACGIH® will not oppose their use in this manner, if the use of TLVs® and BEIs® in these instances will contribute to the overall improvement in worker protection. However, the user must recognize the constraints and limitations subject to their proper use and bear the responsibility for such use.

The Introductions to the TLV®/BEI® Book and the TLV®/BEI® Documentation provide the philosophical and practical bases for the uses and limitations of the TLVs® and BEIs®. To extend those uses of the TLVs® and BEIs® to include other applications, such as use without the judgment of an industrial hygienist, application to a different population, development of new exposure/recovery time models, or new effect endpoints, stretches the reliability and even viability of the database for the TLV® or BEI® as evidenced by the individual Documentation.

It is not appropriate for individuals or organizations to impose on the TLVs® or the BEIs® their concepts of what the TLVs® or BEIs® should be or how they should be applied or to transfer regulatory standards requirements to the TLVs® or BEIs®.



Approved by the ACGIH® Board of Directors on March 1, 1988.

Special Note to User

These values are intended for use in the practice of industrial hygiene as guidelines or recommendations to assist in the control of potential workplace health hazards and for no other use. These values are not fine lines between safe and dangerous concentrations and should not be used by anyone untrained in the discipline of industrial hygiene. It is imperative that the user of these values read the Introduction to each section of the TLV®/BEI® Book and be familiar with the Documentation of the TLVs® and BEIs® before applying the recommendations. ACGIH® disclaims liability with respect to the use of the TLVs® and BEIs®.

Statement of Position Regarding the TLVs® and BEIs®

The American Conference of Governmental Industrial Hygienists (ACGIH®) is a private not-for-profit, nongovernmental corporation whose members are industrial hygienists or other occupational health and safety professionals dedicated to promoting health and safety within the workplace. ACGIH® is a scientific association. ACGIH® is not a standards setting body. As a scientific organization, it has established committees that review the existing published, peer-reviewed scientific literature. ACGIH® publishes guidelines known as Threshold Limit Values (TLVs®) and Biological Exposure Indices (BEIs®) for use by industrial hygienists in making decisions regarding safe levels of exposure to various chemical and physical agents found in the workplace. In using these guidelines, industrial hygienists are cautioned that the TLVs® and BEIs® are only one of multiple factors to be considered in evaluating specific workplace situations and conditions.

Each year ACGIH® publishes its TLVs® and BEIs® in a book. In the introduction to the book, ACGIH® states that the TLVs® and BEIs® are guidelines to be used by professionals trained in the practice of industrial hygiene. The TLVs® and BEIs® are not designed to be used as standards. Nevertheless, ACGIH® is aware that in certain instances the TLVs® and the BEIs® are used as standards by national, state, or local governments.

Governmental bodies establish public health standards based on statutory and legal frameworks that include definitions and criteria concerning the approach to be used in assessing and managing risk. In most instances, governmental bodies that set workplace health and safety standards are required to evaluate health effects, economic and technical feasibility, and the availability of acceptable methods to determine compliance.

ACGIH® TLVs® and BEIs® are not consensus standards. Voluntary consensus standards are developed or adopted by voluntary consensus standards bodies. The consensus standards process involves canvassing the opinions, views and positions of all interested parties and then developing a consensus position that is acceptable to these parties. While the process used to develop a TLV® or BEI® includes public notice and requests for all available and relevant scientific data, the TLV® or BEI® does not represent a consensus position that addresses all issues raised by all interested parties (e.g., issues of technical or economic feasibility). The TLVs® and BEIs® represent a scientific opinion based on a review of existing peer-reviewed scientific literature by committees of experts in public health and related sciences.

ACGIH® TLVs® and BEIs® are health-based values. ACGIH® TLVs® and BEIs® are established by committees that review existing published and peer-reviewed literature in various scientific disciplines (e.g., industrial hygiene, toxicology, occupational medicine, and epidemiology). Based on the available information, ACGIH® formulates a conclusion on the level of exposure that the typical worker can experience without adverse health effects. The TLVs® and BEIs® represent conditions under which ACGIH® believes that nearly all workers may be repeatedly exposed without adverse health effects. They are not fine lines between safe and dangerous exposures, nor are they a relative index of toxicology. The TLVs® and BEIs® are not quantitative estimates of risk at different exposure levels or by different routes of exposure.

Since ACGIH® TLVs® and BEIs® are based solely on health factors, there is no consideration given to economic or technical feasibility. Regulatory agencies should not assume that it is economically or technically feasible for an industry or employer to meet TLVs® or BEIs®. Similarly, although there are usually valid methods to measure workplace exposures at TLVs® and BEIs®, there can be instances where such reliable test methods have not yet been validated. Obviously, such a situation can create major enforcement difficulties if a TLV® or BEI® was adopted as a standard.

ACGIH® does not believe that TLVs® and BEIs® should be adopted as standards without full compliance with applicable regulatory procedures including an analysis of other factors necessary to make appropriate risk management decisions. However, ACGIH® does believe that regulatory bodies should consider TLVs® or BEIs® as valuable input into the risk characterization process (hazard identification, dose-response relationships, and exposure assessment). Regulatory bodies should view TLVs® and BEIs® as an expression of scientific opinion.

ACGIH® is proud of the scientists and the many members who volunteer their time to work on the TLV® and BEI® Committees. These experts develop written Documentation that include an expression of scientific opinion and a description of the basis, rationale, and limitations of the conclusions reached by ACGIH®. The Documentation provides a comprehensive list and analysis of all the major published peer-reviewed studies that ACGIH® relied upon in formulating its scientific opinion. Regulatory agencies dealing with hazards addressed by a TLV® or BEI® should obtain a copy of the full written Documentation for the TLV® or BEI®. Any use of a TLV® or BEI® in a regulatory context should include a careful evaluation of the information in the written Documentation and consideration of all other factors as required by the statutes which govern the regulatory process of the governmental body involved.

  • ACGIH® is a not-for-profit scientific association.
  • ACGIH® proposes guidelines known as TLVs® and BEIs® for use by industrial hygienists in making decisions regarding safe levels of exposure to various hazards found in the workplace.
  • ACGIH® is not a standards setting body.
  • Regulatory bodies should view TLVs® and BEIs® as an expression of scientific opinion.
  • TLVs® and BEIs® are not consensus standards.
  • ACGIH® TLVs® and BEIs® are based solely on health factors; there is no consideration given to economic or technical feasibility. Regulatory agencies should not assume that it is economically or technically feasible to meet established TLVs® or BEIs®.
  • ACGIH® believes that TLVs® and BEIs® should NOT be adopted as standards without an analysis of other factors necessary to make appropriate risk management decisions.
  • TLVs® and BEIs® can provide valuable input into the risk characterization process. Regulatory agencies dealing with hazards addressed by a TLV® or BEI® should review the full written Documentation for the numerical TLV® or BEI®.

ACGIH® is publishing this Statement in order to assist ACGIH® members, government regulators, and industry groups in understanding the basis and limitations of the TLVs® and BEIs® when used in a regulatory context. This Statement was adopted by the ACGIH® Board of Directors on March 1, 2002.

TLV®/BEI® Development Process: An Overview

Provided below is an overview of the ACGIH® TLV®/BEI® Development Process. Additional information is available on the ACGIH® website (www.acgih.org). Please also refer to the Process Flowchart (Figure 1).

  1. Under Study: When a substance or agent is selected for the development or revision of a TLV® or BEI®, the appropriate committee places it on its Under Study list. Each committee determines its own selection of chemical substances or physical agents for its Under Study list. A variety of factors is used in this selection process, including prevalence, use, number of workers exposed, availability of scientific data, existence/absence of a TLV® or BEI®, age of TLV® or BEI®, input from the public, etc. The public may offer input to any TLV® or BEI® Committee by e-mail to science@acgih.org.

    The Under Study lists serve as notification and invitation to interested parties to submit substantive data and comments to assist the committees in their deliberations. Each committee considers only those comments and data that address issues of health and exposure, but not economic or technical feasibility. Comments must be accompanied by copies of substantiating data, preferably in the form of peer-reviewed literature. Should the data be from unpublished studies, ACGIH® requires written authorization from the owner of the studies granting ACGIH® permission to (1) use, (2) cite within the Documentation, and (3) upon request from a third party, release the information. All three permissions must be stated/covered in the written authorization. (See endnote for a sample permission statement.) Electronic submission of all information to the ACGIH® Science Group at science@acgih.org is preferred and greatly increases the ease and efficiency with which the committee can consider the comments or data.

    The Under Study list is published each year by February 1 on the ACGIH® website (www.acgih.org/tlv-bei-guidelines/documentation-publications-and-data/under-study-list), in the Annual Reports of the Committees on TLVs® and BEIs®, and later in the annual TLVs® and BEIs® book. In addition, the Under Study list is updated by July 31 into a two-tier list.  

    • Tier 1 entries indicates which chemical substances and physical agents may move forward as an NIC or NIE in the upcoming year, based on their status in the development process.

    • Tier 2 consists of those chemical substances and physical agents that will not move forward, but will either remain on, or be removed from, the Under Study list for the next year.

     

    This updated list will remain in two-tiers for the balance of the year. All updates to the Under Study lists and publication of the two-tier lists are posted on the ACGIH® website (www.acgih.org/tlv-bei-guidelines/documentation-publications-and-data/under-study-list).  

  2. Draft Documentation: One or more members of the appropriate committee are assigned the task of collecting information and data from the scientific literature, reviewing results of unpublished studies submitted for review, and developing a draft TLV® or BEI® Documentation. The draft Documentation is a critical evaluation of the scientific literature relevant to recommending a TLV® or BEI®; however, it is not an exhaustive critical review of all studies but only those pertinent to identifying the critical effect and setting the TLV®. Particular emphasis is given to papers that address minimal or no adverse health effect levels in exposed animals or workers that deal with the reversibility of such effects, or in the case of a BEI®, that assess chemical uptake and provide applicable determinant(s) as an index of uptake. Human data, when available, are given special emphasis. This draft Documentation, with its proposed TLV® or BEI®, is then reviewed and critiqued by additional committee members, and eventually by the full committee. This often results in several revisions to the draft Documentation before the full committee accepts the proposed draft TLV® or BEI® and draft Documentation. The draft Documentation is not available to the public during this stage of the development process and is not released until it is at the Notice of Intended Changes (NIC) stage. Authorship of the Documentation is not disclosed.

  3. Notice of Intended Changes (NIC):
    [Notice of Intent to Establish (NIE): The Physical Agents section of the TLVs® and BEIs® book also uses the term Notice of Intent to Establish (NIE) in addition to NIC. An NIE follows the same development process as an NIC. For purposes of this process overview, only the term NIC is used.]

    When the full committee accepts the draft Documentation and its proposed TLV® or BEI®, the Documentation and proposed values are then recommended to the ACGIH® Board of Directors for ratification as an NIC. If ratified, each proposed TLV® or BEI® is published as an NIC in the Annual Reports of the Committees on TLVs® and BEIs®, which is published in the ACGIH® member newsletter, Today! Online and is also available online for purchase at http://www.acgih.org/store. At the same time, the draft Documentation is made available through ACGIH® Customer Service or online at http://www.acgih.org/store. All information contained in the Annual Reports of the Committees on TLVs® and BEIs® is integrated into the annual TLVs® and BEIs® book, which is usually available to the general public in February or March of each year. Following the NIC ratification by the ACGIH® Board of Directors, interested parties, including ACGIH® members, are invited to provide data and substantive comments, preferably in the form of peer-reviewed literature, on the proposed TLVs® or BEIs® contained in the NIC. Should the data be from unpublished studies, ACGIH® requires written authorization from the owner of the studies granting ACGIH® permission to (1) use, (2) cite within the Documentation, and (3) upon request from a third party,release the information. All three permissions must be stated/covered in the written authorization. (See endnote for a sample permission statement.) The most effective and helpful comments are those that address specific points within the draft Documentation. Changes or updates are made to the draft Documentation as necessary. If the committee finds or receives substantive data that change its scientific opinion regarding TLV® or BEI® values or notations, the committee may revise the proposal(s) and recommend to the ACGIH® Board of Directors that it be retained on the NIC.

    Important Notice: The comment period for an NIC or NIE draft Documentation and its respective TLV(s)®, notation(s), or BEI(s)®, will be limited to a firm 4-month period, running from February 1 to May 31 of each year. ACGIH® has structured the comment period to ensure all comments are received by ACGIH® in time for full consideration by the appropriate committee before its fall meeting. Because of the time required to properly review, evaluate, and consider comments during the fall meetings, any comments received after the deadline of May 31 will not be considered in that year's committee deliberations regarding the outcome for possible adoption of an NIC or NIE. As general practice, ACGIH® reviews all submissions regarding chemical substances and physical agents on the Under Study list, as well as NICs or NIEs, or currently adopted BEI(s)® or TLV(s)®. All comments received after May 31 will be fully considered in the following year. DraftDocumentation will be available for review during the comment period.

    When submitting comments, ACGIH® requires that the submission be limited to 10 pages in length, including an executive summary. The submission may include appendices of citable material not included as part of the 10-page limit. It would be very beneficial to structure comments as follows:

    1. Executive Summary – Provide an executive summary with a limit of 250 words.
    2. List of Recommendations/Actions – Identify, in a vertical list, specific recommendations/actions that are being requested.
    3. Rationale – Provide specific rationale to justify each recommendation/action requested.
    4. Citable Material – Provide citable material to substantiate the rationale.

    The above procedure will help ACGIH® to more efficiently and productively review comments.

  4. TLV®/BEI® and Adopted Documentation: If the committee neither finds nor receives any substantive data that change its scientific opinion regarding an NIC TLV® or BEI® (or notation), the committee may then approve its recommendation to the ACGIH® Board of Directors for adoption. Once approved by the committee and subsequently ratified by the Board, the TLV® or BEI® is published as adopted in the Annual Reports of the Committees on TLVs® and BEIs® and in the annual TLVs® and BEIs® book, and the draft TLV® or BEI® Documentation is finalized for formal publication.

  5. Withdraw from Consideration: At any point in the process, the committee may determine not to proceed with the development of a TLV® or BEI® and withdraw it from further consideration. Substances or physical agents that have been withdrawn from consideration may be reconsidered by placement on the Under Study list (step 1 above).


    Summary:
     There are several important points to consider throughout the above process:

    1. The appropriate method for an interested party to contribute to the TLV® and BEI® process is through the submission of literature that is peer-reviewed and public. ACGIH® strongly encourages interested parties to publish their studies, and not to rely on unpublished studies as their input to the TLV® and BEI® process. Also, the best time to submit comments to ACGIH®is in the early stages of the TLV® and BEI® Development Process, preferably while the substance or agent is on the Under Study list.

       

    2. An additional venue for presentation of new data is an ACGIH®-sponsored symposium or workshop that provides a platform for public discussion and scientific interpretation. ACGIH®encourages input from external parties for suggestions on symposium topics, including suggestions about sponsors, speakers and format. ACGIH® employs several criteria to determine the appropriateness of a symposium. A key criterion is that the symposium must be the most efficient format to present the committee with information that will assist in the scientific judgment used for writing the Documentation and in setting the respective TLVs® or BEIs®. A symposium topic should be suggested while the substance/agent is under study, as symposia require considerable time, commitment, and resources to develop. Symposium topic suggestions submitted while a substance is on the NIC will be considered, but this is usually too late in the decision-making process. A symposium topic will not be favorably considered if its purpose is to provide a forum merely for voicing opinions about existing data. Rather, there must be on-going research, scientific uncertainty about currently available data, or another scientific reason for the symposium. Symposium topic suggestions should be sent to the ACGIH® Science Group (science@acgih.org).

       

    3. ACGIH® periodically receives requests from external parties to make a presentation to a committee about specific substances or issues. It is strictly by exception that such requests are granted. While there are various reasons for this position, the underlying fact is that the committee focuses on data that have been peer-reviewed and published and not on data presented in a private forum. A committee may grant a request when the data is significantly new, has received peer review, is the best vehicle for receipt of the information, and is essential to the committee's deliberations. The presentation is not a forum to merely voice opinions about existing data. In order for a committee to evaluate such a request, the external party must submit a request in writing that, at a minimum, addresses the following elements: (a) a detailed description of the presentation; (b) a clear demonstration of why the information is important to the committee's deliberations; and (c) a clear demonstration of why a meeting is the necessary method of delivery. This request must be sent to the ACGIH® Science Group (science@acgih.org).

      Also, the committee may initiate contact with outside experts (a) to meet with the committee to discuss specific issues or to obtain additional knowledge on the subject, and (b) to provide written input or review of a Documentation. This is only done on an as needed basis, and not as a routine practice.

    4. ACGIH® does not commit to deferring consideration of a new or revised TLV® or BEI® pending the outcome of proposed or ongoing research.

     

    Important dates to consider throughout each calendar year of the TLV®/BEI® Development Process:

    First Quarter:


    Year Round
    :

    • Public comments are accepted. See Note below.

       

    • Committees meet.
    Note: It is recommended that comments be submitted as early as practical, and preferably no later than May 31st to allow sufficient time for their proper consideration/review. This is particularly important for an NIC TLV®/BEI®.

     

    Important Notice: The comment period for an NIC or NIE draft Documentation and its respective TLV(s)®, notation(s), or BEI(s)®, will be limited to a firm 4-month period, running from February 1 to May 31 of each year. (See Important Notice, step 3 above.)

    Third Quarter:


    Fourth Quarter
    : *

    • TLV®/BEI® Committees vote on proposed TLVs®/BEIs® for NIC or final adoption.

       

    • ACGIH® Board of Directors votes on ratification of TLV®/BEI® Committee recommendations.
    * These actions typically occur early in the fourth quarter, but may occur during other periods of the quarter or year.

    Endnote: Sample permission statement granting ACGIH® authorization to use, cite, and release unpublished studies:

     

    [Name], [author or sponsor of the study**] grants permission to ACGIH® to use and cite the documents listed below, and to fully disclose them to parties outside of ACGIH® upon request. Permission to disclose the documents includes permission to make copies as needed.

    Example: Joseph D. Doe, PhD, co-author of the study, grants permission to ACGIH®to use and cite the document listed below, and to fully disclose this document to parties outside of ACGIH®. Permission to disclose the document includes permission to make copies as needed.

    "Effects of Quartz Status on Pharmacokinetics of Intratracheally Instilled Cristobalite in Rats. March 21, 2003."
    **This statement must be signed by an individual authorized to give this permission, and should include contact information such as title and address.

    Last Revised April 2012

 

Introduction to the TLV® Physical Agents

This section presents Threshold Limit Values (TLVs®) for occupational exposure to physical agents of acoustic, electromagnetic, ergonomic, mechanical, and thermal nature. As with other TLVs®, those for physical agents provide guidance on the levels of exposure and conditions under which it is believed that nearly all healthy workers may be repeatedly exposed, day after day, without adverse health effects.

The target organs and health effects of these physical agents vary greatly with their nature; thus, TLVs® are not single numbers, but rather integrations of the measured parameters of the agent, its effects on workers, or both. Due to the many types of physical agents, a variety of scientific disciplines, detection techniques, and instrumentation are applied. Therefore, it is especially important that the physical agents TLVs® be applied only by individuals adequately trained and experienced in the corresponding measurement and evaluation techniques. Given the unavoidable complexity of some of these TLVs®, the most current Documentation of the Physical Agents TLVs® must be consulted when they are applied.

Because of wide variations in individual susceptibility, exposure of an individual at, or even below, the TLV® may result in annoyance, aggravation of a pre-existing condition, or occasionally even physiological damage. Certain individuals may also be hypersusceptible or otherwise unusually responsive to some physical agents at the workplace because of a variety of factors such as genetic predisposition, body mass, age, personal habits (e.g., smoking, alcohol, or other drugs), medication, or previous or concurrent exposures. Such workers may not be adequately protected from adverse health effects from exposures to certain physical agents at or below the TLVs®. An occupational physician should evaluate the extent to which such workers require additional protection.

TLVs® are based on available information from industrial experience, from experimental human and animal studies, and when possible, from a combination of the three, as cited in their Documentation.

Like all TLVs®, these limits are intended for use in the practice of occupational hygiene and should be interpreted and applied only by a person trained in this discipline. They are not intended for use, or for modification for use, 1) in the evaluation or control of the levels of physical agents in the community or 2) as proof or disproof of an existing physical disability.

These values are reviewed annually by ACGIH® for revision or additions as further information becomes available. ACGIH® regularly examines the data related to mutagenicity, cancer, adverse reproductive effects, and other health effects of physical agents. Comments, accompanied by substantive Documentation in the form of peer-reviewed literature, are solicited and should be forwarded to The Science Group, ACGIH® (science@acgih.org).


ACGIH® disclaims liability with respect to the use of TLVs®.

Notice of Intended Changes. Each year, proposed actions for the forthcoming year are issued in the form of a "Notice of Intended Changes" (NIC). These physical agents, with their corresponding values, comprise those for which 1) a limit is proposed for the first time (i.e., Notice of Intent to Establish [NIE]), 2) a change in the Adopted values are proposed, or 3) retention as an NIC is proposed. In each case, the proposals should be considered trial values during the period they are on the NIC. These proposals are ratified by the ACGIH®Board of Directors and will remain as NICs/NIEs for approximately one year following this ratification. If, during the year, the Committee neither finds nor receives any substantive data that changes its scientific opinion regarding the TLVs® for a NIC/NIE physical agent, the Committee may then approve its recommendation to ACGIH® Board of Directors for adoption.

Documentation is available for each of these physical agents and their proposed values.

This notice provides not only an opportunity for comment on these proposals, but it also solicits suggestions for physical agents to be considered for TLVs®, such as those found on the current list of "Physical Agents Under Study." Comments or suggestions should be accompanied by substantiating evidence in the form of peer-reviewed literature forwarded, preferably in electronic format, to The Science Group, ACGIH® (science@acgih.org). Please refer to the "ACGIH® TLV® and BEI® Development Process" that appears in the front section of this book for a detailed discussion covering this procedure and methods for input to ACGIH®.

Definitions. TLV® categories used in this section include the following:
a) Threshold Limit Value–Time Weighted Average (TLV–TWA). The time-weighted average exposure for an 8-hour workday and 40-hour workweek.
b) Threshold Limit Value–Ceiling (TLV–C). Exposure limit that should not be exceeded even instantaneously.

Carcinogenicity. The Threshold Limit Values for Physical Agents (TLV®-PA) Committee will apply, as necessary, the carcinogenicity designations developed by the Threshold Limit Values for Chemical Substances (TLV®-CS) Committee. Refer to “Appendix A: Carcinogenicity” in the Chemical Substances section of this TLVs® and BEIs® book for these classifications.

Physical and Chemical Factors. Combinations of such physical factors as heat, ultraviolet and ionizing radiation, humidity, abnormal pressure (altitude), and the like, as well as the interaction of physical factors with chemical substances in the workplace, may place added stress on the body so that the effects from exposure at a TLV® may be altered. This stress may act adversely to increase the toxic response to a foreign substance. Although most TLVs® have built-in uncertainty factors to guard against adverse health effects when there are moderate deviations from normal environments, the uncertainty factors for most exposures are not of such a magnitude as to compensate for gross deviations. In such instances, informed professional judgment must be exercised in the proper adjustment of the TLVs®.