Airborne concentrations monitoring

Figure 3.2 shows results of the experiment in which the initial concentration of stable I2 was 0.013 /ug m-3. The scrubber was not in operation. All results are corrected for radioactive decay of 132I. The airborne concentration rose initially as the source was mixed in the air within the containment shell. The activity on the charcoal-loaded papers was due mainly to inorganic iodine, and this declined with a half-life of about 30 min, as 132I was adsorbed on surfaces. Plaques of various materials were exposed periodically to monitor the deposition. In other experiments with more iodine carrier, loss by deposition was more rapid. 

The residues and metabolites of a substance can be measured in an organism or an environmental medium. Alternatively, biological effects known as biomarkers that are known to be the result of exposure to a hazard can be used to determine exposure levels [131]. In some cases, monitoring biomarkers in employees (e.g., metabolites in urine) can prove cheaper than measuring airborne concentrations of a substance in the workplace [132],... 

Microbial pesticides are evaluated for toxicity and infectivity prior to making regulatory decisions. As traditional dose-response-based risk assessments are not considered appropriate for microbial pesticides, regulatory jurisdictions do not typically require occupational and bystander exposure data. However, a small number of studies have monitored airborne concentrations (colony forming units/m ) of microbial pesticides following application (Teschke et al 2001), and the utility of these data should be considered by the regulatory community. 

The need for improved sampling and analytical techniques for monitoring employee exposure extends to substances other than the trace metals. The "no detectable limit philosophy for occupational exposure to carcinogens dates back to the 1974 situation with vinyl chloride in which NIOSH recommended that airborne concentrations be reduced "to levels not detectable by the recommended method (1 ppm) (16). Very low maximum permissible exposure levels are likely to be recommended in the future for substances which are determined to be potential human carcinogens. 

The environmental scientist has at his disposal a variety of sensitive, multi-elemental analytical methods that can lead to a massive amount of data on airborne metals. Optimum use of these tools for environmental monitoring calls for focusing resources only on those metals that are environmentally important. Considerations of toxicity along with their ability to interact in the air, leading to the formation of secondary pollutants, and their presence in air have led to the identification of 17 environmentally important metals nickel, beryllium, cadmium, tin, antimony, lead, vanadium, mercury, selenium, arsenic, copper, iron, magnesium, manganese, titanium, chromium, and zinc. In addition to the airborne concentration, the particle size of environmentally important metals is perhaps the major consideration in assessing their importance. 

Employees are frequently monitored when working in an environment where exposure to toxic metals is a possibility. The most common form of monitoring involves quantification of airborne concentrations of metals in the production process. Threshold limit values for airborne concentrations and time-interval exposure concentrations are defined by the U.S. National Institute for Occupational Safety and Health (NIOSH) to ensure worker safety. Workers may also be monitored by quantification of biological samples. The most common sample used is a random urine sample, and results are expressed in concentration units for the metal of interest per gram of creatinine to normalize for... 

Noble gas collection. The radioactive argon, krypton, and xenon radioisotopes are monitored near nuclear power plants and related facilities to determine the magnitude of releases of gases generated by fission or neutron activation. Radon radioisotopes and their particulate progeny are measured in homes and mines to determine whether their airborne concentrations are below radiation protection limits. 

Regular instrumental monitoring of airborne concentrations is not usually justified or practical in laboratories but may be appropriate when testing or redesigning hoods or other ventilation devices (12) or when a highly toxic substance is stored or used regularly (e.g., 3 times/week) (13). 

If the results of the initial assessment are negative (airborne concentrations were all below the action level of 30 pg/m ), no further monitoring is required. The results of the initial assessment need to be documented in writing. Further monitoring needs to be conducted only if a change in the process, controls, or personnel could result in an increased exposure to lead. 

Ceiling limit is an airborne concentration of a toxic substance in the work environment that should not be exceeded. In threshold limit value (TLV) and permissible exposure limit (PEL), or recommended exposure limit (REL), the maximum allowable concentration to which an employee may be exposed. If instantaneous monitoring is not feasible, then the ceiling is a 15-minute time-weighted average exposure not to be exceeded at any time during the working day. 

Cover the general requirements for monitoring to determine asbestos exposure levels. Each employer who has a work operation where exposure monitoring is reqiiired must perform monitoring to determine the airborne concentrations of asbestos to which employees could be exposed. Determinations of employee exposure have to be made from breathing zone air samples that are representative of the 8-hour TWA and 30-minute short-term exposures of each employee. 

Environmental monitoring for biochemicals has also received attention. Behizad et al. developed a prototype on-line sensing technique for protease and other biochemicals. The monitor was tested in a detergent factory environment and demonstrated to be sensitive and rapid. It could well be a useful development enabling enzyme airborne concentrations, well below the 0.4 pg/m exposure standard (see 11.4.4.4), to be detected, detected. 

Engineering controls must be implemented so that skin contact is minimized or even eliminated. Closed processing systems in factories and dust control measures can help to reduce airborne concentrations of particulate pitch compounds, including PAHs. The current Occupational Safety and Health Administration (OSHA) standard for CTP Vs is 0.2 mg/m of workplace air during an 8-h day, 40-h workweek. Industries that manufacture or use pitch as an end product are monitored periodicaUy by the OSHA to insure that the working environment is maintained within this parameter (Gorman and Liss 1984). 

Behavior includes aU the visible characteristics displayed by a chemical. PCB is a viscous to mobile, colorless to brown hquid that slowly spreads when spilled, depending on the ambient temperature and exact formulation. Indoor spills usually occur in small quantities on concrete, and the vapor will adsorb onto walls, carpeting, drapery, and metal objects. AU forms of exposure should be avoided and the airborne concentration carefiiUy monitored. On the other hand, outdoor spUls can range from a few drops from transformers to fuU trader tanks and can take place on either land or water. 

Initial monitoring. Each employer who has a workplace or work operation covered by this standard shall perform initial monitoring to determine accurately the airborne concentrations of MDA to which employees may be exposed unless ... 

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