hygiene walk-through survey. other sources of basic characterization information include worker interviews, observing exposure tasks, material safety data sheets, workforce scheduling, production data, equipment and maintenance schedules to identify potential exposure agents and people possibly exposed. the information that needs to be gathered from sources should apply to the specific type of work from which the hazards can come from. as mentioned previously, examples of these sources include interviews with people who have worked in the field of the hazard, history and analysis of past incidents, and official reports of work and the hazards encountered. of these, the personnel interviews may be the most critical in identifying undocumented practices, events, releases, hazards and other relevant information. once the information is gathered from a collection of sources, it is recommended for these to be digitally archived (to allow for quick searching) and to have a physical set of the same information in order for it to be more accessible. one innovative way to display the complex historical hazard information is with a historical hazards identification map, which distills the hazard information into an easy to use graphical format. sampling measurements of noise levels using a sound level meter is a component of the occupational hygiene assessment.an occupational hygienist may use one or a number of commercially available electronic measuring devices to measure noise, vibration, ionizing and non-ionizing radiation, dust, solvents, gases, and so on. each device is often specifically designed to measure a specific or particular type of contaminant. electronic devices need to be calibrated before and after use to ensure the accuracy of the measurements taken and often require a system of certifying the precision of the instrument. collecting occupational exposure data is resource- and time-intensive, and can be used for different purposes, including evaluating compliance with government regulations and for planning preventive interventions. the usability of occupational exposure data is influenced by these factors: data storage (e.g. use of electronic and centralized databases with retention of all records) standardization of data collection collaboration between researchers, safety and health professionals and insurers in 2018, in an effort to standardize industrial hygiene data collection among workers compensation insurers and to determine the feasibility of pooling collected ih data, ih air and noise survey forms were collected. data fields were evaluated for importance and a study list of core fields was developed, and submitted to an expert panel for review before finalization. the final core study list was compared to recommendations published by the american conference of governmental industrial hygienists (acgih) and the american industrial hygiene association (aiha). data fields essential to standardizing ih data collection were identified and verified. the "essential" data fields are available and could contribute to improved data quality and its management if incorporated into ih data management systems. canada and several european countries have been working to establish occupational exposure databases with standardized data elements and improved data quality. these databases include mega, colchic, and cwed. dust sampling nuisance dust is considered to be the total dust in air including inhalable and respirable fractions. various dust sampling methods exist that are internationally recognised. inhalable dust is determined using the modern equivalent of the institute of occupational medicine (iom) mre 113a monitor (see section on workplace exposure, measurement & modelling). inhalable dust is considered to be dust of less than 100 micrometers aerodynamic equivalent diameter (aed) that enters through the nose and or mouth. see lungs respirable dust is sampled using a cyclone dust sampler design to sample for a specific fraction of dust aed at a set flow rate. the respirable dust fraction is dust that enters the 'deep lung' and is considered to be less than 10 micrometers aed. nuisance, inhalable and respirable dust fractions are all sampled using a constant volumetric pump for a specific sampling period. by knowing the mass of the sample collected and the volume of air sampled, a concentration for the fraction sampled can be given in milligrams (mg) per metre cubed (m3). from such samples, the amount of inhalable or respirable dust can be determined and compared to the relevant occupational exposure limits. by use of inhalable, respirable or other suitable sampler (7 hole, 5 hole, et cetera), these dust sampling methods can also used to determine metal exposure in the air. this requires collection of the sample on a methyl-cellulose ester (mce) filter and acid digestion of the collection media in the laboratory followed by measuring metal concentration though an atomic absorption (or emission) spectrophotometry. both the uk health and safety laboratory and niosh manual of analytical methods have specific methodologies for a broad range of metals in air found in industrial processing (smelting, foundries, et cetera). a further method exists for the determination of asbestos, fibreglass, synthetic mineral fibre and ceramic mineral fibre dust in air. this is the membrane filter method (mfm) and requires the collection of the dust on a grided filter for estimation of exposure by the counting of 'conforming' fibres in 100 fields through a microscope. results are quantified on the basis of number of fibres per millilitre of air (f/ml). many countries strictly regulate the methodology applied to the mfm. chemical sampling two types of chemically absorbent tubes are used to sample for a wide range of chemical substances. traditionally a chemical absorbent 'tube' (a glass or stainless steel tube of between 2 and 10 mm internal diameter) filled with very fine absorbent silica (hydrophilic) or carbon, such as coconut charcoal (lypophylic), is used in a sampling line where air is drawn through the absorbent material for between four hours (minimum workplace sample) to 24 hours (environmental sample) period. the hydrophilic material readily absorbs water-soluble chemical and the lypophylic material absorbs non water-soluble materials. the absorbent material is then chemically or physically extracted and measurements performed using various gas chromatograph or mass spectrometry methods. these absorbent tube methods have the advantage of being usable for a wide range of potential contaminates. however, they are relatively expensive methods, are time consuming and require significant expertise in sampling and chemical analysis. a frequent complaint of workers is in having to wear the sampling pump (up to 1 kg) for several days of work to provide adequate data for the required statistical certainty determination of the exposure. in the last few decades, advances have been made in 'passive' badge technology. these samplers can now be purchased to measure one chemical (e.g. formaldehyde) or a chemical type (e.g. ketones) or a broad spectrum of chemicals (e.g. solvents). they are relatively easy to set up and use. however, considerable cost can still be incurred in analysis of the 'badge'. they weigh 20 to 30 grams and workers do not complain about their presence. unfortunately 'badges' may not exist for all types of workplace sampling that may be required, and the charcoal or silica method may sometimes have to be applied. from the sampling method, results are expressed in milligrams per cubic meter (mg/m3) or parts per million (ppm) and compared to the relevant occupational exposure limits. it is a critical part of the exposure determination that the method of sampling for the specific contaminate exposure is directly linked to the exposure standard used. many countries regulate both the exposure standard, the method used to determine the exposure and the methods to be used for chemical or other analysis of the samples collected. noise sampling two types of noise are environmental noise, which is unwanted sound that occurs outdoors, and occupational noise, the sound that is received by employees while they are in the workplace. environmental noise can originate from various sources depending on the activity, location, and time. environmental noise can be generated from transportation such as road, rail, and air traffic, or construction and building services, and even domestic and leisure activities. there is a legal limit on noise that the environmental noise is 70 db(a) over 24-hours of average exposure. similarly, the limit of occupational noise is 85 db(a) per niosh, or 90 db(a) per osha for an 8-hour work period. in order to enforce these limits, these are the methods to measure noise, including sound level meter (slm), sound level meter app, integrating sound level meter (islm), impulse sound level meter (impulse slm), noise dosimeter, and personal sound exposure meter (psem). sound level meter (slm) measures the sound level at a single point of time and consequently requires multiple measurements to be taken at different times of the day. the slm is primarily used for measuring relatively stable sound levels; there is increased difficulty in measuring the average sound exposure if the noise levels vary greatly. sound level meter app is a program that can be downloaded to a mobile device. it receives noise through the phone’s built-in or external microphone and displays the sound level measurement from the app’s sound level meters and noise dosimeters. integrating sound level meter (islm) measures the equivalent sound levels within the measurement period. because the islm measures noise in a particular area, it is difficult to measure a worker’s personal exposure as they move throughout a workspace. impulse sound level meter (impulse slm) measures the peak of each sound impulse. the most optimal conditions to measure the peaks occur when there is little background noise. noise dosimeter collects the sound level for a given point in time, as well as different sound levels across time. the noise dosimeter can measure personal exposure levels and can be used in the areas with a high risk of fire. personal sound exposure meter (psem) is worn by employees while they work. the advantage of the psem is that it eliminates the need for noise assessors to follow up with workers when the assessors measure the noise levels of the work areas. excessive noise can lead to occupational hearing loss. 12% of workers report having hearing difficulties, making this the third most common chronic disease in the u.s. among these workers, 24% have hearing difficulties caused by occupational noise, with 8% affected by tinnitus, and 4% having both hearing difficulties and tinnitus. ototoxic chemicals including solvents, metals, compounds, asphyxiants, nitriles, and pharmaceuticals, may contribute further to hearing loss. exposure management and controls the hierarchy of control defines the approach used to reduce exposure risks protecting workers and communities. these methods include elimination, substitution, engineering controls (isolation or ventilation), administrative controls and personal protective equipment. occupational hygienists, engineers, maintenance, management and employees should all be consulted for selecting and designing the most effective and efficient controls based on the hierarchy of control. professional societies the development of industrial hygiene societies originated in the united states, beginning with the first convening of members for the american conference of governmental industrial hygienists in 1938, and the formation of the american industrial hygiene association in 1939. in the united kingdom, the british occupational hygiene society started in 1953. through the years, professional occupational societies have formed in many different countries, leading to the formation of the international occupational hygiene association in 1987, in order to promote and develop occupational hygiene worldwide through the member organizations. the ioha has grown to 29 member organizations, representing over 20,000 occupational hygienists worldwide, with representation from countries present in every continent. peer-reviewed literature there are several academic journals specifically focused on publishing studies and research in the occupational health field. the journal of occupational and environmental hygiene (joeh) has been published jointly since 2004 by the american industrial hygiene association and the american conference of governmental industrial hygienists, replacing the former american industrial hygiene association journal and applied occupational & environmental hygiene journals. another seminal occupational hygiene journal would be the annals of occupational hygiene, published by the british occupational hygiene society since 1958. further, the national institute for occupational safety and health maintains a searchable bibliographic database (nioshtic-2) of occupational safety and health publications, documents, grant reports, and other communication products. the hierarchy of controls is an important tool to determine how to control hazards most efficiently and effectively in a workplace. occupational hygiene as a career examples of occupational hygiene careers include: compliance officer on behalf of regulatory agency professional working on behalf of company for the protection of the workforce consultant working on behalf of companies researcher performing laboratory or field occupational hygiene work education the basis of the technical knowledge of occupational hygiene is