The threshold limit value (TLV) is believed to be a level to which a worker can be exposed per shift in the worktime without adverse effects. Strictly speaking, TLV is a reserved term of the American Conference of Governmental Industrial Hygienists (ACGIH). TLVs issued by the ACGIH are the most widely accepted occupational exposure limits both in the United States and most other countries.However, it is sometimes loosely used to refer to other similar concepts used in occupational health and toxicology, such as acceptable daily intake (ADI) and tolerable daily intake (TDI). Concepts such as TLV, ADI, and TDI can be compared to the no-observed-adverse-effect level (NOAEL) in animal testing, but whereas a NOAEL can be established experimentally during a short period, TLV, ADI, and TDI apply to human beings over a lifetime and thus are harder to test empirically and are usually set at lower levels. TLVs, along with biological exposure indices (BEIs), are published annually by the ACGIH.
The TLV is an estimate based on the known toxicity in humans or animals of a given chemical substance, and the reliability and accuracy of the latest sampling and analytical methods. It is not a static definition since new research can often modify the risk assessment of substances and new laboratory or instrumental analysis methods can improve analytical detection limits. The TLV is a recommendation by ACGIH, with only a guideline status. As such, it should not be confused with exposure limits having a regulatory status, like those published and enforced by the Occupational Safety and Health Administration (OSHA). The OSHA regulatory exposure limits permissible exposure limits (PELs) published in 29CFR 1910.1000 Table Z1 are based on recommendations made by the ACGIH in 1968, although other exposure limits were adopted more recently. Many OSHA exposure limits are not considered by the industrial hygiene community to be sufficiently protective levels since the toxicological basis for most limits have not been updated since the 1960s. The National Institute for Occupational Safety and Health (NIOSH) publishes recommended exposure limits (RELs) which OSHA takes into consideration when promulgating new regulatory exposure limits.
The TLV for chemical substances is defined as a concentration in air, typically for inhalation or skin exposure. Its units are in parts per million (ppm) for gases and in milligrams per cubic meter (mg/m3) for particulates such as dust, smoke and mist. The basic formula for converting between ppm and mg/m3 for gases is ppm = (mg/m^3) * 24.45 / molecular weight. This formula is not applicable to airborne particles.
Three types of TLVs for chemical substances are defined:
There are TLVs for physical agents as well as chemical substances. TLVs for physical agents include those for noise exposure, vibration, ionizing and non-ionizing radiation exposure and heat and cold stress.
The TLV and most other occupational exposure limits are based on available toxicology and epidemiology data to protect nearly all workers over a working lifetime. Exposure assessments in occupational settings are most often performed by Occupational / Industrial Hygiene (OH/IH) professionals who gather "Basic Characterization" consisting of all relevant information and data related to workers, agents of concern, materials, equipment and available exposure controls. The exposure assessment is initiated by selecting the appropriate exposure limit averaging time and "decision statistic" for the agent. Typically the statistic for deciding acceptable exposure is chosen to be the majority (90%, 95% or 99%) of all exposures to be below the selected occupational exposure limit. For retrospective exposure assessments performed in occupational environments, the "decision statistic" is typically a central tendency such as the mean or geometric mean or median for each worker or group of workers. Methods for performing occupational exposure assessments can be found in "A Strategy for Assessing and Managing Occupational Exposures, Third Edition Edited by Joselito S. Ignacio and William H. Bullock".
The TLV is equivalent in spirit to various occupational exposure limits developed by organizations around the world; however, the materials covered, values recommended, and definitions used can differ amongst organizations. These occupational exposure limits include:
The opposite of "safe enough for any length of time" is "not safe for any length of time", and IDLH values are defined for concentrations of substances that are immediately dangerous to life or health.
Isocyanate is the functional group with the formula R−N=C=O. Organic compounds that contain an isocyanate group are referred to as isocyanates. An organic compound with two isocyanate groups is known as a diisocyanate. Diisocyanates are manufactured for the production of polyurethanes, a class of polymers.
The American Conference of Governmental Industrial Hygienists (ACGIH) is a professional association of industrial hygienists and practitioners of related professions, with headquarters in Cincinnati, Ohio. One of its goals is to advance worker protection by providing timely, objective, scientific information to occupational and environmental health professionals.
Occupational hygiene is the anticipation, recognition, evaluation, control, and confirmation of protection from hazards at work that may result in injury, illness, or affect the well being of workers. These hazards or stressors are typically divided into the categories biological, chemical, physical, ergonomic and psychosocial. The risk of a health effect from a given stressor is a function of the hazard multiplied by the exposure to the individual or group. For chemicals, the hazard can be understood by the dose response profile most often based on toxicological studies or models. Occupational hygienists work closely with toxicologists for understanding chemical hazards, physicists for physical hazards, and physicians and microbiologists for biological hazards Environmental and occupational hygienists are considered experts in exposure science and exposure risk management. Depending on an individual's type of job, a hygienist will apply their exposure science expertise for the protection of workers, consumers and/or communities.
The permissible exposure limit is a legal limit in the United States for exposure of an employee to a chemical substance or physical agent such as high level noise. Permissible exposure limits are established by the Occupational Safety and Health Administration (OSHA). Most of OSHA's PELs were issued shortly after adoption of the Occupational Safety and Health (OSH) Act in 1970.
Acute toxicity describes the adverse effects of a substance that result either from a single exposure or from multiple exposures in a short period of time. To be described as acute toxicity, the adverse effects should occur within 14 days of the administration of the substance.
Chloroprene is the common name for 2-chlorobuta-1,3-diene (IUPAC name) with the chemical formula CH2=CCl−CH=CH2. Chloroprene is a colorless volatile liquid, almost exclusively used as a monomer for the production of the polymer polychloroprene, a type of synthetic rubber. Polychloroprene is better known as Neoprene, the trade name given by DuPont.
2-Butoxyethanol is an organic compound with the chemical formula BuOC2H4OH (Bu = CH3CH2CH2CH2). This colorless liquid has a sweet, ether-like odor, as it derives from the family of glycol ethers, and is a butyl ether of ethylene glycol. As a relatively nonvolatile, inexpensive solvent, it is used in many domestic and industrial products because of its properties as a surfactant. It is a known respiratory irritant and can be acutely toxic but animal studies did not find it to be mutagenic, and no studies suggest it is a human carcinogen. A study of 13 classroom air contaminants conducted in Portugal reported a statistically significant association with increased rates of nasal obstruction, the study also reported a positive association below the level of statistical significance with a higher risk of obese asthma and increased child BMI.
Hydrogen selenide is an inorganic compound with the formula H2Se. This hydrogen chalcogenide is the simplest and most commonly encountered hydride of selenium. H2Se is a colorless, flammable gas under standard conditions. It is the most toxic selenium compound with an exposure limit of 0.05 ppm over an 8-hour period. Even at extremely low concentrations, this compound has a very irritating smell resembling that of decayed horseradish or 'leaking gas', but smells of rotten eggs at higher concentrations.
Exposure assessment is a branch of environmental science and occupational hygiene that focuses on the processes that take place at the interface between the environment containing the contaminant of interest and the organism being considered. These are the final steps in the path to release an environmental contaminant, through transport to its effect in a biological system. It tries to measure how much of a contaminant can be absorbed by an exposed target organism, in what form, at what rate and how much of the absorbed amount is actually available to produce a biological effect. Although the same general concepts apply to other organisms, the overwhelming majority of applications of exposure assessment are concerned with human health, making it an important tool in public health.
An occupational exposure limit is an upper limit on the acceptable concentration of a hazardous substance in workplace air for a particular material or class of materials. It is typically set by competent national authorities and enforced by legislation to protect occupational safety and health. It is an important tool in risk assessment and in the management of activities involving handling of dangerous substances. There are many dangerous substances for which there are no formal occupational exposure limits. In these cases, hazard banding or control banding strategies can be used to ensure safe handling.
1-Bromopropane (n-propylbromide or nPB) is an organobromine compound with the chemical formula CH3CH2CH2Br. It is a colorless liquid that is used as a solvent. It has a characteristic hydrocarbon odor. Its industrial applications increased dramatically in the 21st century.
An Exposure Action Value (EAV) or Action Value (AV) is a limit set on occupational exposure to noise where, when those values are exceeded, employers must take steps to monitor the exposure levels. These levels are measured in decibels. The American Occupational Safety and Health Administration (OSHA) set the EAV to 85 dB(A). When the eight-hour time-weighted average (TWA) reaches 85 dB(A), employers are required to administer a continuing, effective hearing conservation program. The program consists of monitoring, employee notification, observation, an audiometric testing program, hearing protectors, training programs, and record keeping requirements.
Karl Bernhard Lehmann was a German hygienist and bacteriologist born in Zurich. He was a brother to publisher Julius Friedrich Lehmann (1864–1935).
Manure management refers to capture, storage, treatment, and utilization of animal manures in an environmentally sustainable manner. It can be retained in various holding facilities. Animal manure can occur in a liquid, slurry, or solid form. It is utilized by distribution on fields in amounts that enrich soils without causing water pollution or unacceptably high levels of nutrient enrichment. Manure management is a component of nutrient management.
A short-term exposure limit (STEL) is the acceptable average exposure over a short period of time, usually 15 minutes as long as the time-weighted average is not exceeded.
Tolerable weekly intake (TWI) estimates the amount per unit body weight of a potentially harmful substance or contaminant in food or water that can be ingested over a lifetime without risk of adverse health effects. TWI is generally preceded by "provisional" to indicate insufficient data exists, increasing uncertainty. The term TWI should be reserved for when there is a well-established and internationally accepted tolerance, backed by sound and uncontested data. Although similar in concept to tolerable daily intake (TDI), which is of the same derivation of acceptable daily intakes (ADIs), TWI accounts for contaminants that do not clear the body quickly and may accumulate within the body over a period of time. An example is heavy metals such as arsenic, cadmium, lead, and mercury. The concept of TWI takes into account daily variations in human consumption patterns.
The American Industrial Hygiene Association (AIHA) is a 501(c)6 non-profit organization, whose mission is "Creating knowledge to protect worker health." The American Industrial Hygiene Association works to provide information and resources to Industrial Hygienists and Occupational Health professionals.
The respiratory protective devices (RPD) can protect workers only if their protective properties are adequate to the conditions in the workplace. Therefore, specialists have developed criteria for the selection of proper, adequate respirators, including the Assigned Protection Factors (APF) - the decrease of the concentration of harmful substances in the inhaled air, which to be provided with timely and proper use of a certified respirator of certain types (design) by taught and trained workers, when the employer performs an effective respiratory protective device programme.
There are unique occupational health issues in the casino industry. The most common are from cancers resulting from exposure to second-hand tobacco smoke, and musculoskeletal injury (MSI) from repetitive motion injuries while running table games over many hours.