Lowest effect concentration level

LOAEC/L Lowest-observed-adverse-effect concentration/level. The lowest level of exposure to a chemical in a test that causes statistically significant differences from the controls in a measured negative response. 

LOEC/L Lowest-observed-effect concentration/level. The lowest concentration of an agent used in a toxicity test that has a statistically significant effect on the exposed population of test organisms, compared with the controls. 

The classification of category 1, 2, or 3 cannot take into account the extremely variable potential for developmental toxicity. Therefore, in some countries efforts are being made to implement a better differentiation system. The German MAK commission, for example, classifies the developmental toxic substances in 3 additional groups on the basis of the occupational exposure levels (OEL). A classification has to be done if a developmental toxic effect can occur at the concentration of the established occupational exposure level. As a consequence of the fact that the concentration of the OEL is mostly much lower than the lowest effect concentration (LOEL) for developmental toxicity, many substances classified as developmental toxic substances do not show this property at the OEL. Figure 3.12 shows some selected chemicals which do not cause concern at the OEL. 

Tables (3-1, 3-2, and 3-3) and figures (3-1 and 3-2) are used to summarize health effects and illustrate graphically levels of exposure associated with those effects. These levels cover health effects observed at increasing dose concentrations and durations, differences in response by species, minimal risk levels (MRLs) to humans for noncancer end points, and EPA s estimated range associated with an upper- bound individual lifetime cancer risk of 1 in 10,000 to 1 in 10,000,000. Use the LSE tables and figures for a quick review of the health effects and to locate data for a specific exposure scenario. The LSE tables and figures should always be used in conjunction with the text. All entries in these tables and figures represent studies that provide reliable, quantitative estimates of No-Observed-Adverse-Effect Levels (NOAELs), Lowest-Observed-Adverse-Effect Levels (LOAELs), or Cancer Effect Levels (CELs).

The toxicity requirements are established per type of industry, in terms of the maximum number of times the effluents needs to be diluted to produce a no observed effect concentration (NOEC), defined as Gf for fish, Gd for daphnia, Ga for algae, and G1 for luminescent bacteria. Testing is limited to the exposure to only the appropriate Gx level, which should not produce any observed effect [the G-value corresponds with the dilution of the effluent, expressed as the lowest dilution factor (1,2,4,...) causing less than 10% mortality]. The level of maximum allowable toxicity per industrial branch is based on the level that is considered to be attainable with state-of-the-art process and/or treatment technology. Violating the toxicity requirements results in a levy, which makes state-of-the-art compliance a more economic option [12]. 

Peroxides are a very common impurity in many excipients, particularly polymeric excipients [56]. They are used as initiators in polymerisation reactions, but are difficult to remove. Ding [57] monitored the peroxide concentrations within polysorbate 80 solutions, and demonstrated the effect of light, heat and concentration on peroxide concentrations. The author showed that the peroxide concentrations increased 9-fold at the lowest polysorbate concentration versus increases of only 1.5-fold at the highest polysorbate concentration. However, the absolute peroxide levels at the higher concentration were much higher. 

Table II includes supporting data for greater-than-additive inhibition of alfalfa apparent photosynthetic rates induced by SO2+NO2 mixtures. The enhanced effects were most marked at the lower concentrations applied, becoming less pronounced as pollutant levels were raised. At 50 pphm of each gas no synergism was evident. At this SO2 exposure concentration, sulfur dioxide appeared to regulate the observed plant responses. Significant amounts of inhibition resulted from the lowest bipollutant concentrations used (15 pphm of each gas) these concentrations were well below those required for the individual pollutants to measurably suppress apparent photosynthesis rates. At these exposure levels where no tissue necrosis occurred, the plants recovered completely within 2 hr after fumigation. The manner by which this inhibiting interaction occurred is not well understood. This pollutant combination is also known to act in a synergistic fashion to cause visible injury to plants, and further study of this mixture may be warranted.

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