Toxicity measurements threshold limit values

TLV is the threshold limit value, and the inverse is a measure of inhalation toxicity potential for a chemical. Values taken from NIOSH Pocket Guide to Chemical Hazards (http //www.cdc.gov/niosh/npg/npg.html), and the Specialized Information Service of the National Library of Medicine (NLM) (http //sis.nlm.nih.gov/). 

Data to assess the potential of JP-8 to adversely affect reproduction and development are sparse. One study (Puhala et al. 1997) reported measurements of human exposures and the values for the components of jet fuels analyzed that were far below the TWA threshold limit values (see Tabel A-2). Data on the absorption of volatile hydrocarbon components of JP-8 suggest that systemic exposure is likely, by any route of exposure. The single published developmental toxicity study (Cooper and Mattie 1996) did not report an adverse effect on embryonic or fetal development in rats with oral treatment at up to 2,000 mg/kg/d on days 6-15 of pregnancy, except for a decrease in body weight of offspring. 

Hence, organic solvents should be handled with care. In the USA, the threshold limit values [TL values) are used as a measure of the inhalation toxicity for chronic interaction with solvent vapours [90]. In the Federal Republic of Germany, the maximum concentration values at the workplace [MAK values) are used [91, 92]. Threshold limit values refer to airborne concentrations of substances and represent conditions under which it is believed that workers may be repeatedly exposed daily without adverse effect. They refer to time-weighted average concentrations for a normal 8-hour workday... 

Respirators provide protection against inhaling harmful materials. Different types of respirators may be used depending on the level of protection desired. For example, supplied-air respirators (e.g., a self-contained breathing apparatus) may be required in situations where the presence of highly toxic substances is known or suspected and/or in confined spaces where it is likely that toxic vapors may accumulate. On the other hand, a full-face or half-face air-purifying respirator may be used in situations where measured air concentrations of identified substances will be reduced by the respirator below the substance s threshold limit value (TLV) and the concentration is within the service limit of the respirator (i.e., that provided by the canister). 

Carbon dioxide is toxic, can be an asphyxiant by virtue of oxygen displacement (described above), and can cause death due to paralysis of the respiratory centres (Hoather and Wright, 1989). The threshold limit value for CO2 is 0.5% and concentrations above 5% result in laboured breathing, headaches and visual disturbances. The long term occupational exposure limit (OEL) is 5,000 vpm and the short term occupational exposure limit (STEL) is 1.5% by volume. In most situations arising from landfill gas-associated problems, carbon dioxide toxicity will only occur when collection in an enclosed environment occurs. Under these conditions there would also be potential for explosion due to potentially high methane levels and gas control measures would be required to alleviate such a potentially dangerous situation. 

RTECS-4 (toxic compounds) these were 269 compounds for which time-weighted average and control hmit Threshold Limit Values (TLVs) in ppm are available. The data are continuous and were converted into a measure of toxicity, T, given by... 

Toxic and essential trace elements intakes were computed from food consumption data of the population in northern Italy and element concentration measurements. The results (Table 10.6) were compared with the Italian Recommended Dietary Allowance (RDA) for essential trace elements and with the Provisional Tolerable Daily/Weekly Intake (PTDI/PTWI) for toxic elements. Finally, an assessment was made of the extent to which each food contributes to the total intake of trace elements by the population under study and the most contaminated foods were also detected. On the whole, mean intake values satisfied the Italian RDA for all the essential trace elements [31], while the potentially toxic trace elements were below the relevant threshold limits. 

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