Occupational threshold levels

The need for control of formaldehyde emission from UF-bonded wood products has been recognized since Wittmann (4) reported in 1962 that extensive use of particleboard in furniture and building envelopes can cause indoor formaldehyde concentrations exceeding occupational threshold levels. However, it proved to be difficult to define the problem because formaldehyde emission from finished products was not regularly measured, and the correlation between emission rate and the environmental factors were not yet well established. 

Inasmuch as the indoor environment has the purpose to shelter occupants of buildings, it intrinsically tends to confine indoor pollutants. Sofar some 300 such pollutants have been identified (10) and, as mentioned earlier, radon and formaldehyde ( may reach occupational threshold levels. Indoor air quality is controlled by a... 

Several countries and agencies have responded to formaldehyde complaints by setting indoor air formaldehyde limits. As indicated above, these limits are usually arrived at by modifying the occupational threshold levels by a factor of ten. A short summary of such levels is shown in Table IV ... 

Recommendations for cadmium in air and human health protection under the worst scenario (Table 1.8) assume that total daily air intake is 27.14 m3 for an adult human who spends about 6.3 h in occupational exposure to air containing 100 pg Cd/m3 (USEPA 1980). Under these conditions, a 70-kg adult would retain about 361 pg Cd/day, based on an absorption factor of 0.5 (USEPA 1980), and most of this cadmium would probably be translocated to the kidney a critical threshold level of 200 mg Cd/kg in the kidney would be reached in about 1.52 years. It is not now known... 

NIOSH recommends that the occupational exposure level not exceed 100 pg/m3 for a 10-hour TWA workday (NIOSH 1992). In addition, the American Conference of Governmental Industrial Hygienists has recommended a time-weighted average threshold limit value (TWA-TLV) of 100 pg/m3 for occupational exposure to diazinon (ACGIH 1986). 

Ventilation is often adopted as a control measure to keep VOCs and C02 below specified threshold levels. The effect of operation of the ventilation system on spatial and temporal profiles is illustrated from two separate buildings. With adequate ventilation, the C02 levels are easily controlled within threshold levels. However, VOCs present a problem due to their build-up overnight between the time of ventilation shutdown after office hours and its reactivation in the morning just before occupancy. Purging the building as an effective means to reduce the exposure risks is discussed and illustrated. Some concluding remarks on other changes to indoor exposures are made at the end of the chapter. 

All bulk elemental analysis methods, such as NAA and FAAS, suffer from the serious disadvantage of lack of specificity in that the elements detected are not unique to FDR but also occur from occupational and environmental sources. Many surveys were carried out to determine background levels of lead, antimony, and barium on the hands of people not involved with firearms. Some surveys also included copper and mercury. Both general and occupational data were gathered and threshold levels established for each of the elements. The threshold level may be defined as the level above which the results may be significant and correlate to the discharge of a firearm. The best that could be stated was that the levels detected were consistent with the discharge of a firearm but could not be taken as conclusive proof of the presence of FDR. 

Seki Y, Urashima Y, Aikawa H, et al. 1975. [Trichloro-compounds in the urine of humans exposed to methyl chloroform at sub-threshold levels.] Arch Arbeitsmedizin-Int Arch Occup Health 34 39-49. (German)... 

The subcommittee further concludes that in addition to inhalation exposures, the potential exists for a substantial contribution to the overall JP-8 exposure by the dermal route, including mucous membranes and the eyes, either by contact with vapors and aerosols or by direct skin contact with JP-8. It should be noted that earlier this year, the American Conference of Governmental Industrial Hygienists proposed a Threshold Limit Value for kerosene and j et fuels, as a total hydrocarbon vapor, of200 mg/m3.2 Also, ExxonMobil Biomedical Sciences, Inc., has set an occupational exposure level of 5 mg/m3 for kerosene and middle distillate fuel aerosols.3... 

To stay below the threshold levels for radiation damage, the National Committee on Radiation Protection and Measurement recommends the following standards for occupational conditions in controlled areas ... 

If any of the ingredients which do not exceed the concentration limits in the previous paragraph could be released fiom the mixture such that they could exceed an established OSHA PEL, or an ACGIH threshold level value, or could represent an occupational health hazard, their chemical and common rrames must be given as well. The same information is also required for any ingredient in the mixture which poses a physical hazard (as opposed to a health hazard). 

Open up an occupational medicine textbook from the late twentieth century and the table of contents will likely read like a list of chemicals. Each chemical has a threshold level value at which it becomes toxic and a description of the effects caused in the human body once that threshold is passed. There are no portraits of the factory floor or labor conditions. There are no tales of family hardship. Instead, these descriptions are written in a specialized language originating in laboratories, where the techniques of toxicology rendered industrial chemicals measurable. Crack open toxicology to find out how it connected chemicals to bodies. 

Threshold Limit Values or Occupational Exposure Limits (preferably with reference to their interpretation, i.e. not as safe levels). 

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