- Email: [email protected]
Alternatives for the no-observed-effect level
376
Selected bibliography
gas-phase chemistry scheme is used. Particular emphasis is given to the study of how the ozone and hydrogen peroxide levels are affected. Significant changes in the distributions are found when aqueous-phase chemical reactions are included. The result is loss of ozone in the aqueous phase, with pronounced reductions in ozone levels in the middle and lower troposphere. Ozone levels are reduced by 10 to 30% with the largest reductions in the remote middle troposphere, bringing the values in better agreement with observations. Changes in H,O,? are harder to predict. Although, in one case study, hydrogen peroxide is produced within the aqueous phase, concentrations are mostly comparable or even lower than in the other cases. Hydrogen peroxide levels are, however, shown to be very pH sensitive. pH values around 5 seem to favour high H,O, levels.. High H,Oz concentrations may be found particularly in the upper part of the clouds under favourable conditions. Comparative uptake kinetics and transport of cadmium and phosphate in Phleum pratense-Glomus deserticohun associations.
Arnold P. T. and Kapustka L. A. Ecological Planning Toxicology, Inc., 5010 SW Hout Street, Corvallis OR 97333-9540 USA. Environ. Toxicol. Chem. 1993 12(l) 177-186. Summ. in Engl. Mycorrhizal plants (timothy grass, Phleum pratense with Glomus deserticolum) were compared to nonmycorrhizal timothy grass to determine the effect of the mycorrhizal condition on the uptake and transport of cadmium. Companion experiments were conducted to ascertain phosphate uptake kinetics of mycorrhizal and nonmycorrhizal plants. Divalent cation competition experiments also were employed in this study. Comparisons of the high-affinity uptake mechanisms between mycorrhizal and nonmycorrhizal plants identified higher levels of phosphate uptake were due to an increase in the number of uptake sites rather than to differences in affinity. The respective values for K(m) for highaffinity phosphate uptake were 2.5 f 1.3 pM P (mycorrhizal) and 3.4 f 1.3 pM P (nonmycorrhizal), but these values were not statistically different at the (Y = 0.05 level. Highaffinity Cd’+ uptake differed significantly between mycorrhizal (4.5 f 2.8 pM) and nonmycorrhizal (2.8 + 1.1 pM) plants. Presence of Ca2’ at 1.0 mM concentration conferred considerable competitive protection in both the mydorrhizal and the nonmycorrhizal conditions. The effect of Ca2+ was an approximate fourfold increase in the respective K(m) values. Alternatives
for the no-observed-effect
level. Hoekstra
J. A.
and Van Ewijk P. H. of Public Health, Environmental National Institute Protection, PO Box 1, 3720 BA Bilthoven, The Netherlands. Environ. Toxicol. Chem. 1993 12(l) 187-194. Summ. in Engl. This paper questions the usefulness of the no-observed-effect level (NOEL) as a summary statistic for ecotoxicological experiments. Quantification of the NOEL depends critically on size and variability of an experiment: smaller and less precise experiments lead to higher values for the NOEL, which gives the wrong signal to suppliers of a NOEL. The NOEL will generally lie in a dose range where possible effects cannot be excluded, even within the context of the experiment. Hence it does not form a suitable starting point for extrapolation to field situations. Alternative methods of finding a dose with a negligible effect are discussed. A two-step procedure is proposed that involves finding the dose whose effect is at most 25%, followd by linear extrapolation to a dose whose effect is acceptably small. The procedure leads to higher values if efforts are made to increase the power of the experiment.
Perspective: Defining lead as the premiere environmental health issue for children In America: Criteria and their quantitative
application. Mushak P. Metal Toxicology and Risk Assessment, (Adjunct) Department of Pathology, University of North Carolina, 8 11 Onslow Street, Durham, NC 27705, USA. Environ. Res. 1992 59(2) 281-309. Summ. in Engl. The principal environmental health issue for American children is pervasive lead poisoning from the many decades of lead contamination. Available scientific evidence cementing lead’s premiere ranking is voluminous, multifaceted, and compelling. This evidence, however, requires organization into a clear and coherent body of science before it can be fully recognized or comprehended by either the scientific community or the general public and its representatives: public health officials, regulators, policy makers, and legislators. An attempt at such organization is presented and begins with the premise that there exist clear, objective criteria by which a premiere environmental health issue can be defined. A second premise is that these criteria sort themselves into three categories which cover the full spectrum of toxic contaminantpopulation relationships. They are: (1) economic and sociopolitical, (2) scientific and public health, and (3) societal risk assessment criteria. The first set of criteria includes economic and historical centrality, primacy of economic over public health considerations, a relatively narrow decision-making framework, and controlled flow of information on the toxicant, especially its negative impacts. The second set of criteria is also orthodox in scope: the toxicant should be indestructible, should accumulate in both the environment and the body, and should be a multimedia contaminant; it should produce toxicity in numerous organs with little impediment; toxicity should be produced with low/no threshold in huge numbers of the most vulnerable; and finally, effects should persist in the critical target organ(s). There is a third, more globally encompassing, set of criteria important for present-day requirements for risk assessment; e.g., the contaminant should produce full-spectrum population-wide as well as individual toxicity. Evidence for societal harm should be compelling. It should typify the increasing importance of the elements of preventive over clinical medicine and the substance should bring to bear the costbenefit analysis of macro plus micro health risk. Lead exposure and toxicity is conclusively shown to meet ALL of these criteria and is the premiere environmental health threat to America’s children.
Environmental Bssessment of tihutyltin in Canada. Maguire R. J. Rivers Research Branch, National Water Research Institute, Dept Environ/Centre Inland Waters, Burlington, Ont. L7R 4A6 Canada. Water Sci. Technol. 1992 26(12) 125-132. Summ. in Engl.
A global three-dimensional model of the stratospheric acid layer. Golombek A. and Prinn R. G.
sulfuric
Center for Global Change Science, Massachusetts Inst. of Technology, Cambridge, MA 02139, USA. J. Amos. Chem. 1993 16(2) 179-199. Summ. in Engl.
The history of air pollution in York, England. Brimblecombe P. and Bowler C. Department of Atmospheric Chemistry, School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, UK. J. Air Waste Munage. Assoc. 1992 42(12) 1562-1566. Summ. in Engl.
Selected bibliography
gas-phase chemistry scheme is used. Particular emphasis is given to the study of how the ozone and hydrogen peroxide levels are affected. Significant changes in the distributions are found when aqueous-phase chemical reactions are included. The result is loss of ozone in the aqueous phase, with pronounced reductions in ozone levels in the middle and lower troposphere. Ozone levels are reduced by 10 to 30% with the largest reductions in the remote middle troposphere, bringing the values in better agreement with observations. Changes in H,O,? are harder to predict. Although, in one case study, hydrogen peroxide is produced within the aqueous phase, concentrations are mostly comparable or even lower than in the other cases. Hydrogen peroxide levels are, however, shown to be very pH sensitive. pH values around 5 seem to favour high H,O, levels.. High H,Oz concentrations may be found particularly in the upper part of the clouds under favourable conditions. Comparative uptake kinetics and transport of cadmium and phosphate in Phleum pratense-Glomus deserticohun associations.
Arnold P. T. and Kapustka L. A. Ecological Planning Toxicology, Inc., 5010 SW Hout Street, Corvallis OR 97333-9540 USA. Environ. Toxicol. Chem. 1993 12(l) 177-186. Summ. in Engl. Mycorrhizal plants (timothy grass, Phleum pratense with Glomus deserticolum) were compared to nonmycorrhizal timothy grass to determine the effect of the mycorrhizal condition on the uptake and transport of cadmium. Companion experiments were conducted to ascertain phosphate uptake kinetics of mycorrhizal and nonmycorrhizal plants. Divalent cation competition experiments also were employed in this study. Comparisons of the high-affinity uptake mechanisms between mycorrhizal and nonmycorrhizal plants identified higher levels of phosphate uptake were due to an increase in the number of uptake sites rather than to differences in affinity. The respective values for K(m) for highaffinity phosphate uptake were 2.5 f 1.3 pM P (mycorrhizal) and 3.4 f 1.3 pM P (nonmycorrhizal), but these values were not statistically different at the (Y = 0.05 level. Highaffinity Cd’+ uptake differed significantly between mycorrhizal (4.5 f 2.8 pM) and nonmycorrhizal (2.8 + 1.1 pM) plants. Presence of Ca2’ at 1.0 mM concentration conferred considerable competitive protection in both the mydorrhizal and the nonmycorrhizal conditions. The effect of Ca2+ was an approximate fourfold increase in the respective K(m) values. Alternatives
for the no-observed-effect
level. Hoekstra
J. A.
and Van Ewijk P. H. of Public Health, Environmental National Institute Protection, PO Box 1, 3720 BA Bilthoven, The Netherlands. Environ. Toxicol. Chem. 1993 12(l) 187-194. Summ. in Engl. This paper questions the usefulness of the no-observed-effect level (NOEL) as a summary statistic for ecotoxicological experiments. Quantification of the NOEL depends critically on size and variability of an experiment: smaller and less precise experiments lead to higher values for the NOEL, which gives the wrong signal to suppliers of a NOEL. The NOEL will generally lie in a dose range where possible effects cannot be excluded, even within the context of the experiment. Hence it does not form a suitable starting point for extrapolation to field situations. Alternative methods of finding a dose with a negligible effect are discussed. A two-step procedure is proposed that involves finding the dose whose effect is at most 25%, followd by linear extrapolation to a dose whose effect is acceptably small. The procedure leads to higher values if efforts are made to increase the power of the experiment.
Perspective: Defining lead as the premiere environmental health issue for children In America: Criteria and their quantitative
application. Mushak P. Metal Toxicology and Risk Assessment, (Adjunct) Department of Pathology, University of North Carolina, 8 11 Onslow Street, Durham, NC 27705, USA. Environ. Res. 1992 59(2) 281-309. Summ. in Engl. The principal environmental health issue for American children is pervasive lead poisoning from the many decades of lead contamination. Available scientific evidence cementing lead’s premiere ranking is voluminous, multifaceted, and compelling. This evidence, however, requires organization into a clear and coherent body of science before it can be fully recognized or comprehended by either the scientific community or the general public and its representatives: public health officials, regulators, policy makers, and legislators. An attempt at such organization is presented and begins with the premise that there exist clear, objective criteria by which a premiere environmental health issue can be defined. A second premise is that these criteria sort themselves into three categories which cover the full spectrum of toxic contaminantpopulation relationships. They are: (1) economic and sociopolitical, (2) scientific and public health, and (3) societal risk assessment criteria. The first set of criteria includes economic and historical centrality, primacy of economic over public health considerations, a relatively narrow decision-making framework, and controlled flow of information on the toxicant, especially its negative impacts. The second set of criteria is also orthodox in scope: the toxicant should be indestructible, should accumulate in both the environment and the body, and should be a multimedia contaminant; it should produce toxicity in numerous organs with little impediment; toxicity should be produced with low/no threshold in huge numbers of the most vulnerable; and finally, effects should persist in the critical target organ(s). There is a third, more globally encompassing, set of criteria important for present-day requirements for risk assessment; e.g., the contaminant should produce full-spectrum population-wide as well as individual toxicity. Evidence for societal harm should be compelling. It should typify the increasing importance of the elements of preventive over clinical medicine and the substance should bring to bear the costbenefit analysis of macro plus micro health risk. Lead exposure and toxicity is conclusively shown to meet ALL of these criteria and is the premiere environmental health threat to America’s children.
Environmental Bssessment of tihutyltin in Canada. Maguire R. J. Rivers Research Branch, National Water Research Institute, Dept Environ/Centre Inland Waters, Burlington, Ont. L7R 4A6 Canada. Water Sci. Technol. 1992 26(12) 125-132. Summ. in Engl.
A global three-dimensional model of the stratospheric acid layer. Golombek A. and Prinn R. G.
sulfuric
Center for Global Change Science, Massachusetts Inst. of Technology, Cambridge, MA 02139, USA. J. Amos. Chem. 1993 16(2) 179-199. Summ. in Engl.
The history of air pollution in York, England. Brimblecombe P. and Bowler C. Department of Atmospheric Chemistry, School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, UK. J. Air Waste Munage. Assoc. 1992 42(12) 1562-1566. Summ. in Engl.