Threshold activity value

Sara tide III, section 313, Clean Air Act 1990, threshold limit values, and LD qS ate given in Table 3 for the substances for which data are available. Additional information is continuously being developed to provide guidelines for the safe handling of dye carriers and carrier-active chemicals. 

Dimethyl carbamoyl chloride is a direct-acting alkylating agent with a wide spectrum of genotoxic activity." ACGIH has classified dimethyl carbamoyl as A2-a suspected human carcinogen with no threshold limit value (TLV). 

Hansen LF, Nielsen GD Sensory irritation and pulmonary irritation of -methyl ketones Receptor activation mechanisms and relationships with threshold limit values. Arch Toxicol 68 193-202, 1994... 

Nonane was not mutagenic in bacterial assays with or without metabolic activation. The 2003 ACGIH threshold limit value-time-weighted average (TLV-TWA) is 200 ppm (1050mg/m ). 

In the majority of the studies on the composition of food aromas, AEDA is used for the determination of the relative odour potency of the compounds detected by GC-O (reviewed in [1]). The odour potency is proportional to the odour activity value (OAV) of the compound in air. The OAV is defined as the ratio of the concentration of a compound to its odour threshold [3]. 

Odorant Concentration (pg/kg) Threshold (pg/kg water) Odour activity value ... 

Odour activity values were calculated by dividing the concentrations of the odorants by their orthonasal odour thresholds in water... 

A word here on the toxicity of V compds The compds act chiefly as irritants to the con-junctivae and respiratory tract, turning the tongue green. Exptl biochemical studies show that V compds inhibit cholesterol synthesis and the activity of the enzyme cholinesterase. Prolonged exposure to V compds may lead to fatal pulminary involvement. The Threshold Limiting Values of these compds, in particular the highly toxic pentoxide, are dust, 0.5mg/CM fumes, 0.05mg/CM (Refs 7,16 18)... 

Odor activity values The number of times an odorant is present above its threshold as measured in the food matrix... 

Reliable quantitative data are a prerequisite for evaluating the contribution of a single odorant to a positive aroma or off-flavor. They are needed to calculate odor activity values (OAV) that are defined as the ratio of the concentration to the sensory threshold of a given compound in a matrix (Rothe and Thomas, 1963 Acree et al., 1984). These values give guidance in the evaluation of the impact of an odorant to the overall aroma profile. 

Odour thresholds and odour activity values (OAV) of important pastry odorants (PB butter pastry PM margarine pastry) [441 ... 

During AEDA, interactions between the odorants are not taken into consideration, since every odorant is evaluated individually. Therefore, it may be possible that odorants are recognized which are possibly masked in the food flavor by more potent odorants. Furthermore, the odor activity values only partially reflect the situation in the food, since OAVs are mostly calculated on the basis of odor thresholds of single odorants in pure solvents. However, in the food system, the threshold values may be influenced by nonvolatile components such as lipids, sugars or proteins. The following examples will indicate that systematic sensory model studies are important further steps in evaluating the contribution of single odorants to the overall food aroma. 

In an alcohol-free beer, the concentrations of the beer odorants were 5 to 10-fold lower than in the pale lager beer [18] suggesting that the former beer is a very appropriate matrix for the determination of odor thresholds. A determination of the odor thresholds in the alcohol-free beer revealed (Table 15) that, compared to water, the odor threshold of all odorants increased, but to a different extent. For instance, the threshold of (E)-B-damascenone increased by a factor of 2500, while that of HDF was enhanced only by a factor of eight. Odor activity values calculated on the basis of the odor thresholds in the alcohol-free beer (Table 15) now confirmed the significant contribution of HDF to the dark beer flavor. 

An example of a nonoccupational exposure is methanol, which is formed endogenously, probably as the result of the activities of intestinal flora or enzymatic processes. It is present in a number of consumer products. Methanol may be present in low concentrations in some foods, juices, and alcoholic beverages. Methanol can also be derived from the intestinal enzymatic hydrolysis of the artificial sweetener aspartame, which results in methanol absorption from the intestine (Butchko et al. 2002). It is estimated that a 355-mL serving of aspartame-sweetened beverages and of various fruit and tomato juices may contribute about 20-100 mg of dietary methanol (Butchko et al. 2002). For comparison purposes, exposure at the current Threshold Limit Value time-weighted average of methanol (262 mg/m3) would result in a daily dose of about 1,500 mg, assuming an 8-hour inhaled volume of 10 m3 of air and absorption of 57%. 

One way to quantify the odor impact of a compound is to determine the aroma value or odor activity value (OAV). This is calculated by dividing the concentration of the compound by its perception threshold. Therefore, the odor impact of a compound increases in proportion to its OAV when this value is >1. Thus, compounds exhibiting higher OAV values are more likely to contribute to the aroma of wine and have an important influence on its sensory characteristics. 

Fogliano et al.72 have prepared melanoidin [molecular mass (MM) >12 kDa] from glucose-glycine, lactose-lysine, and lactose-iV-acetyllysine lactose-lysine proved to be the odd one out, exhibiting less than one-tenth the absorbance of the other two at 460 and 520 nm. Their CAVs (colour activity value,73 defined as the ratio of a colorant s concentration to its visual detection threshold, both in pg kg-1) were 8000, 200, and 4000, respectively. Examination by MALDI-TOF gave results only for the lactose-A-acetyllysine melanoidin, with peaks around 6,12, and 24 kDa (the spectrum reproduced by Borrelli et al.74 shows peaks around 6, 7.5, and 12 kDa). The antioxidant effects of the melanoidins were also examined (see p. 129). 

In many ways, colour, which is a sensation, should be assessed visually. On analogy with the treatment of odorants, Hofmann73 has taken a crucial step in this area by defining a colour dilution factor (CD) and a colour activity value (CAV). CD is the factor required for any solution of a colorant x to be diluted to its colour threshold. CAVX is the ratio of the concentration of x (jug kg-1) to its threshold concentration (jug kg-1)- The colour contribution of a component colorant to the colour of a mixture can then be defined as... 

The intensity of aroma compounds found by AEDA and CHARM may be determined with further accuracy by subjecting them to odor unit (also called odor activity value) measurement.71,72 This is done by first measuring the odor threshold of a compound while the concentration of this compound in the specimen is determined using internal standards (for instance, isotopic samples in contemporary approach). Dividing the latter concentration with the odor threshold will give the odor unit value, naturally being higher when a compound better contributes to the total aroma. 

Human exposure to JP-8 occurs during refueling and defueling operations and mechanical activities that deal with storage, transfer, and combustion. The most likely exposure of military personnel is via inhalation of aerosolized or vaporized fuel however, topical and oral exposures also are possible. Occupational exposure standards are based on knowledge of the toxicity of components of JP-8. Those few exposure values that are published suggest that human exposures were below ACGIH TWA threshold limit values for those chemicals. 

Lys °]LSK, with a threshold concentration value of 2.0 0.4 x 10" ° M, representing a retention of fully 65% of parent fragment activity and 430% of the activity of the full-length peptide ([Nle ]LSK). Thus, basicity at the 10 position is a critical factor for LSK-receptor site interaction. Conversely, [4-11,... 

---