Priority Existing Chemical
m)Effects on Organisms in the Environment
Download 0.91 Mb.
|
- Navigate this page:
- Table 14. Summary of aquatic toxicity data for MMT and Manganese
m)Effects on Organisms in the EnvironmentThis section provides information on the effects of MMT and Mn, the predominant combustion by-product, on animals and plants. Based on MMT use patterns, the review of effects has included the potential effects to organisms typically inhabiting terrestrial and aquatic environments. The following information on MMT has been obtained from Kem-Tech Laboratories (1977) and Analytical Bio-chemistry Laboratories, Inc. (1990). Information on Mn, a component of MMT, has been obtained from various sources but principally the United States Environmental Protection Agency (USEPA) Ecotox Database (USEPA, May 2000) and the Australian and New Zealand Water Quality Guidelines (ANZECC and ARMCANZ, 2000). As these reference sources on Mn have been peer-reviewed, all of the publications referenced from these sources have not been peer reviewed for this present report (see citation for specific reference sources). Table 14 provides a summary of toxicity test data for aquatic organisms. Table 14. Summary of aquatic toxicity data for MMT and Manganese
m.1Terrestrial animalsm.1.1MMTKinetics/metabolism and toxicity of MMT to mammals (e.g. rats, mice, monkeys, rabbits) have been presented in Sections 9 and 10, respectively. No information was available on the potential effects of excessive MMT exposure to birds or other terrestrial organisms. m.1.2ManganeseMammalian toxicity data for inorganic Mn compounds resulting from MMT combustion have been presented in Section 11. No information was available on the potential effects of excessive Mn exposure to birds or other terrestrial organisms. m.2Terrestrial plantsm.2.1MMTNo information was available on the toxicity of MMT to terrestrial plants. m.2.2ManganeseManganese is an essential trace element for micro-organisms, plants and animals (CCREM, 1987, as cited by ANZECC and ARMCANZ, 2000). It is involved in nitrogen assimilation, as a catalyst in plant metabolism and functions with iron in the synthesis of chlorophyll (Labanauskas, 1966, as cited by Efroymson et al., 1997). Toxicity symptoms include marginal chlorosis and necrosis of leaves and root browning. Excess Mn interferes with enzymes, decreases respiration and is involved in the destruction of auxin (Foy et al., 1995, as cited in Efroymson et al., 1997). Plant uptake of soil Mn occurs mainly via the roots of plants. However, intake through leaves may also contribute a fraction of the total uptake, and leaf uptake is slower (May, 1998). Fertilizer application of Mn to crops and other plants is undertaken to correct Mn deficiency by either soil or foliage application. Most Mn in soils is precipitated as Mn oxide or hydroxide; however, the Mn2+ ion is the form available to plants. Soil Mn recommendations are based on the soil pH and crop being grown. Excessive soil Mn may be problematic in acid soils (approximately pH <4.8; Rosen and Eliason, 2002). A toxic Mn situation may also develop in plants if excessive soil and/or foliar applications are used. Foliar-applied Mn fertilizer in excess of recommended amounts for Mn deficiency adjustment, or in small volumes of water, may burn leaves of plants (e.g. wheat, oats and sugar beets; Ohio State University, 1996). In the early stages of plant growth, Mn toxicity symptoms may be similar to deficiency symptoms (e.g. interveinal chlorosis). Spotting, scorching on leaf margins and cupping of leaves are also typical toxicity symptoms. In potatoes, the symptoms are chlorosis and black specks on the stems and undersides of the leaves, followed by death of the lower leaves. Crops, including alfalfa, cabbage, cauliflower, clover, dry edible beans, potatoes, small grains, sugar beets and tomatoes, are sensitive to excess Mn. Plant tissue analysis is used to diagnose Mn status in plants. Values below 20 mg/kg are usually considered deficient. Readings of 30 to 200 mg/kg are normal, and those over 300 mg/kg may lead to adverse effects. Liming soils to the desired pH range for the crop will usually prevent soil Mn toxicity. Soil Mn may be classified by concentrations as follows: Very High >400 mg/kg, High 201 to 400 mg/kg, Medium 51 to 200, Low 25 to 50 mg/kg and Very Low <25 mg/kg (Stanley and Baker, 2002). Efroymson et al. (1997) has established soil (bulk) and soil solution toxicity benchmarks for Mn of 500 mg/kg in soil and 4 mg/L in soil solution. Wallace et al. (1977) evaluated the effects of Mn, added as MnSO4 to a loam soil, on leaf and stem weights of bush beans grown from seed for 17 days. Stem weight was reduced 29% by 500 mg Mn/kg. This was the lowest concentration tested. As the 500 mg/kg benchmark for Mn is based on this one study, confidence in the benchmark is low; however, confidence in the soil solution benchmark is higher as more data are available (Efroymson et al., 1997). As indicated above, soil Mn toxicity is a function of soil pH as well as Mn concentration. No published phytotoxicity data were available on the acceptable concentration of Mn in air for terrestrial plants. Recommended rates for foliar Mn fertilizers vary but range between approximately 0.008 and 2 kg Mn/ha, and frequent applications may be required (Vitosh, 1990; Barmac, 2002). Recommended foliar concentrations also vary but approximate 0.7 to 1.1 mg Mn/L (Barmac, 2002). The information available indicates that Mn is an essential nutrient for plants and of low toxicity but exposure to high to very high soil Mn concentrations, combined with low pH soil conditions, or excessive foliar Mn may lead to adverse effects in plants. Adverse effects arise mainly due to excessive soil Mn bioavailability and toxicity from foliar application is unlikely.
Directory: data -> assets -> word doc -> 0020 word doc -> Commonwealth of Australia 2002 word doc -> Commonwealth of Australia 2000 word doc -> Rail safety news issue 6 – October 2011 word doc -> Review of Multiple Chemical Sensitivity: Identifying word doc -> Board Endorsed October 2009 amended 13-09-11 with extra units 0020 -> Rail safety news issue 5 may 2011 0020 -> The arts ripple effect: valuing the arts in communities 0020 -> Monash university accident research centre report documentation page 0020 -> Section 1: Working with the Government and the Parliament 6 1Summary 6 0020 -> Bachelor of Computer Science and Bachelor of Economics (61010) Applicability of the general provisions 11 47. 1 Download 0.91 Mb. Share with your friends:
| ||||||||||||||||||||||||||||||||||||