Toxicological thresholds

The outputs from risk assessment will normally include information about the relationship between dose and risk and estimates of levels of doses and thus risks in the population. For contaminants that have a toxicological threshold the Provisional Tolerable Weekly Intake (PTWI) might be defined and the number of consumers who have the potential to exceed this level of intake quantified. If a PTWI cannot be established (such as for genotoxic carcinogens) then it may be possible to quantify the proportion of a population exposed to a given level of risk by using QRA methods. If QRA methods cannot be applied then a qualitative assessment can be made such as to reduce intake levels to as low as is reasonably practicable. In either case it is the function of risk management to identify an optimal course of action to minimise the risk to consumers. 

The hormetic dose-response can predict harm below or above the toxicological threshold, and thus it is consistent with positive and negative outcomes, unlike the LNT or the S-shaped models. 

The hormetic dose-response model can predict the occurrence of beneficial responses below the toxicological threshold. This can be seen with endpoints such as enhanced longevity, decreased disease incidence, and improved cognition, unlike the threshold and linear at low-dose (LNT) models. 

Other Substances. Driving under the influence of alcohol cases are compHcated because people sometimes consume alcohol with other substances (11—13). The most common iUicit substances taken with alcohol are marijuana and cocaine (see Table 1) (14). In combination with alcohol, some dmgs have an additive effect. When a blood or urine alcohol sample is tested for alcohol and the result is well below the legal concentration threshold yet the test results are not consistent with the arresting officers observation that the subject was stuporous, further toxicological tests for the possible presence of dmgs are indicated. 

The threshold limit value (TLV) for cyclohexane is 300 ppm (1050 mg/m ). With prolonged exposure at 300 ppm and greater, cyclohexane may cause irritation to eyes, mucous membranes, and skin. At high concentrations, it is an anesthetic and narcosis may occur. Because of its relatively low chemical reactivity, toxicological research has not been concentrated on cyclohexane. 

American Conference of Governmental Industrial Hygienists (ACGIH), Documentation of Threshold Limit Values, 3rd ed. 1971, pp. 16 and 245-246 F. A, Patty in Industrial Hygiene and Toxicology, Interscience Publishers, New York, Vol. II, 2nd ed., 1963, Chap. 24. 

The most frequently used reference guidelines for ambient particulate concentration are those of WHO, the EU, and the USEPA. These guidelines are based on clinical, toxicological, and epidemiologic evidence and were established by determining the concentrations with the lowest observed adverse effect (implicitly accepting the notion that a lower threshold exists under which no adverse human... 

Health Hazards Information - Information included are recommended personal protective equipment for hazard materials handling specialist, typical symptoms following exposure to the chemical, general first aid treatment procedures, and various toxicological information including toxicity by ingestion, inhalation and short term exposures. Additional information included are the liquid or solid irritant characteristics and odor threshold data. 

The general subject of toxicologj is discussed in detail in Part III - Chapter 11. However, tliree toxicology teniis are introduced here in order for tlie reader to better grasp tlie problems encountered witli a toxic release. Threshold limit values (TLVs) can be categorized in tliree ways. ... 

Sandahl, J.F, Baldwin, D.H., and Jenkins, J.J. et al. (2005). Comparative thresholds for acetylcholinesterase inhibition and behavioural impairment in Coho Salmon exposed to chlorpyriphos. Environmental Toxicology and Chemistry 24, 136-145. 

The platform includes different decision trees for the following endpoints the estimation of Threshold of Toxicological Concern (TTC), aquatic modes of action [44], skin and eye irritation and corrosion, mutagenicity and carcinogenicity [45], in vivo micronucleus assay, identification of Michael Acceptors and biodegradation potential [46]. 

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