Jerome O. Nriagu

A history of global metal pollution

Pollution caused by heavy metals can be traced back to the Roman Empire. In his Perspective, Nriagu considers the historical record of metal pollution and discusses results published in the same issue by Hong et al. (p. 246) in which ice core records were used to determine the quantity of copper emitted into the atmosphere by ancient smelters.

The rise and fall of leaded gasoline

Abstract Leaded gasoline has become one of the few “environmentally unsafe” products to be forced out of the market place. The history of lead additives in gasoline is outlined, from the discovery of the antiknock properties of tetraethyllead in 1921 (the first gallon of leaded gasoline was sold on 2 February 1923 to a motorist in Dayton, Ohio), to recent measures to remove lead from the gasoline of the 1980s. This report provides an historical backdrop to the continuing debate on environmental lead pollution.

Isotopic record of lead pollution in lake sediments from the northeastern United States

Abstract Although it is common knowledge that Pb concentrations have increased in lake sediments in the northeastern United States over the last 150 years, the processes responsible have been the subject of debate. In this study, differences in lead isotopic compositions and concentrations in sediment from large lakes (Lake Erie, Ontario, and Michigan) and small ones (Deep Lake and Lake Andrus) are used to infer temporal changes in the source(s) of anthropogenic Pb in the Great Lakes region. A natural (background) component of Pb is present in sediment deposited prior to 1860 in Lake Erie and the other lakes as indicated from low Pb concentrations and uniform lead isotopic compositions. Changes in isotopic ratios of lake sediment reflect differing sources of anthropogenic Pb superimposed on the natural component such as regional deforestation from 1860–1890 followed by coal combustion and ore smelting through 1930. Combustion of leaded gasoline was the dominant anthropogenic Pb source to the atmosphere (and by inference to lake sediment) from 1930–1980. Temporal changes in lead isotopic compositions in lake sediment suggest that the source of the Pb used in gasoline additives gradually changed from 1930 to present. The best example is a distinct shift in lead isotopic ratios in lake sediment deposited after 1970 which corresponds to increased Pb production from the Viburnum Trend deposits in Missouri (present in all lakes except Ontario). However, the changes in lead isotopic compositions are much less variable than and do not parallel those calculated on the basis of annual United States mine production and imports. Rather, anthropogenic recycling of Pb as well as natural mixing processes during emission, transport, and deposition of Pb in lake sediment control most of the variation in lead isotope ratios. Differences in lead isotopic ratios in Lake Michigan, Erie, and Deep Lake sediment preserve regional differences in lead isotopic ratios from U.S. and Canadian sources first noted in aerosols by Sturges and Barrie (1987). More localized sources of Pb (such as point discharges) are needed to explain the results from Lake Ontario and Andrus.

Oxidation of arsenite in groundwater using ozone and oxygen.

Oxidation of arsenite [As(III)] with ozone and oxygen was investigated in groundwater samples containing 46-62 micrograms/l total dissolved arsenic, 100-1130 micrograms/l Fe and 9-16 micrograms/l Mn. Conversion of As(III), which constituted over 70% of dissolved arsenic in the samples, to As(V) was fast with ozone, but sluggish with pure oxygen and air. Iron and manganese in the samples were also oxidized and, by sequestering the resultant As(V), played a significant role in the rate of reaction. Sorption capacity of freshly precipitated Fe(OH)3 was estimated to be 15.3 mg As/g. The kinetics of As(III) oxidation were interpreted using modified pseudo-first-order reaction. Half-lives of As(III) in experimental solutions involving saturation with each gas were approximately 4 min for the ozone reaction and, depending on the Fe concentrations, 2-5 days for pure oxygen and 4-9 days for air.

Regional differences in worldwide emissions of mercury to the atmosphere

Annual emissions of anthropogenic Hg to the atmosphere in different regions of the world during the last decade show an interesting dichotomy: the emissions in the developed countries increased at the rate of about 4.5–5.5% yr−1 up to 1989 and have since remained nearly constant, while in developing countries the emissions continue to rise steadily at the rate of 2.7–4.5% yr−1. On a global basis, however, the total anthropogenic emissions of Hg increased by about 4% yr−1 during the 1980s, peaked in 1989 at about 2290 t and are currently decreasing at the rate of about 1.3% yr−1. Solid waste disposal through incineration processes is the dominant source of atmospheric mercury in North America (∼ 40%), Central and South America (∼34%), western Europe (∼28%) and Africa (∼30%), whereas coal combustion remains the dominant source in Asia (∼42%) and eastern Europe and the former USSR (∼40%). Mining and smelting of Zn and Pb represent the major industrial source of Hg in Oceania (∼35%).

MOLECULAR ASPECTS OF ARSENIC STRESS

Arsenic produces a variety of stress responses in mammalian cells, including metabolic abnormalities accompanied by growth inhibition and eventually apoptosis. Morphological alterations in cells exposed to arsenic often suggest underlying disruption of cytoskeletal structural elements responsible for cellular integrity, shape, and locomotion. However, specifics of the ultrastructural changes produced by arsenic remain poorly understood. Various tissues and organs differ in their sensitivity to arsenic, with the liver and skin being the most studied. Characteristic skin pathology related to arsenic exposure ranges from hyperkeratotic lesions to squamous-cell carcinomas. However, molecular events in the arsenic-exposed skin still remain to be elucidated. Although mutagenicity of arsenic has not been unequivocally established, recent evidence supports the view that oncogenic mutations do occur, and that only selected enzymes related to DNA replication and repair are affected by arsenic. Sensitivity of the mitotic spindle to arsenic, particularly its organic compounds, underlies the well-documented chromosomal aberrations in arsenic-exposed populations. Arsenite-induced stress at the molecular level shares many features with the heat shock response. This includes the differential sensitivity of the stress signal pathway elements to the magnitude of the stress, stressor-specific activation of the response elements, and the protective role of the heat shock response. Oxidative stress, the central component of heat shock response, is typical of arsenic-related effects that are, in fact, regarded as the chemical paradigm of heat stress. Similar to heat stress, arsenite induces heat shock proteins (HSPs) of various sizes. The signal cascade triggered by arsenitelike heat stress induces the activity of the mitogen-activated protein (MAP) kinases, extracellular regulated kinase (ERK), c-jun terminal kinase (JNK) , and p38. Through the JNK and p38 pathways, arsenite activates the immediate early genes c-fos, c-jun, and egr-1, usually activated by various growth factors, cytokines, differentiation signals, and DNA-damaging agents. Like other oxygen radical-producing stressors, arsenic induces nitric oxide production at the level of transcriptional activation along with induction of poly(ADP)ribosylation, NAD depletion, DNA strand breaks, and formation of micronuclei. This review presents an overview of current research on molecular aspects of arsenic stress with an emphasis on the tissue-specific events in humans. It deals with current progress on the understanding of the signal transduction pathways and mechanisms underlying the sensitivity of various species, organs, and tissues to arsenic.

Toxic metals in the atmosphere.

Emission Factors of Atmospheric Elements (J. M. Pacyna). Atmospheric Trace Elements from Natural and Anthorpogenic Sources (J. M. Pacyna). Sampling and Measurement of Trace Element Emissions from Particulate Control Devices (A.D. Shendrikar & D. S. Emsor). Smelting Operations and Trace Metals in Air and Precipitation in the Sudbury Basin, (W. H. Chan & M. A. Lusis). Emissions and Air Quality Relationships for Atmospheric Trace Metals (G. R. Cass & G. R. McRae). Quantitative Source Attribution of Metals in the Air Using Receptor Models (P. K. Hopke). Trace Metals in the Atmosphere of Rural and Remote Areas (G. B. Wiersma and C. I. Davidson). Trace Metals in the Arctic Aerosol (N. Z. Heidam). Chemical Elements as Tracers of Pollutant Transport to a Rural Area (L. Husain). Chemical Speciation and Reaction Pathways of Metals in the Atomspere, (R. M. Harrison). Characterization of Trace Metal Compounds in the Atmosphere in Terms of Density (A. Sugimae). The Sizes of Airborne Trace Metal-Containing Particles (C. I. Davidson & J. F. Osborn). Metal Solubility in Atmospheric Deposition (D. F. Gatz & L.-C. Chu). Impact of Atmospheric Inputs on the Hydrospheric Trace Metal Cycle (W. Salomons). Atmospheric Toxic Metals and Metalloids in the Snow and Ice Layers Deposited in Greenland and Antarctica from Prehistoric Times to Present (C. F. Boutron). Monitoring the Atmospheric Depostion of Metals by Use of Bog Vegetation and Peat Profiles (W. A. Glooschenko). Mercury Vapor in the Atmosphere: Three Case Studies on Emission, Deposition, and Plant Uptake (S. E.. Lindberg). Biogeochemical Cycling of Organic Lead Compunds (W. R. A. De Jonghe & F. C. Adams). Airbone Lead in the Environment in France (J. Servant).

Lead orthophosphates—IV Formation and stability in the environment

Abstract Experimental and predicted thermochemical constants are used to assess the formation and stability of lead phosphates in soil and sedimentary environments. For the chemical conditions likely to be encountered in oxidizing environments, the stability fields of pyromorphites [Pb5(PO4)3X, X = OH−, Cl−, Br− and F−] and plumbogummite [PbAl3(PO4)2(OH)5-H2O] predominate strongly over those of the other secondary lead minerals. The theoretical phase relationships together with several field observations are used as the basis for suggesting that the interaction of lead and phosphorus (to form pyromorphites and plumbogummite in particular) is an important buffer mechanism controlling the migration and fixation of lead in the environment. Calculations using the concentrations of lead and phosphate ions in serum indicate that the solubility of lead phosphates may be the limiting factor with regard to lead ion concentration in human body. The removal of lead from wastewater by precipitation as lead chloropyromorphite is considered a spin-off of possible industrial interest.

Prevalence of Antibiotic Resistance in Drinking Water Treatment and Distribution Systems

ABSTRACT The occurrence and spread of antibiotic-resistant bacteria (ARB) are pressing public health problems worldwide, and aquatic ecosystems are a recognized reservoir for ARB. We used culture-dependent methods and quantitative molecular techniques to detect and quantify ARB and antibiotic resistance genes (ARGs) in source waters, drinking water treatment plants, and tap water from several cities in Michigan and Ohio. We found ARGs and heterotrophic ARB in all finished water and tap water tested, although the amounts were small. The quantities of most ARGs were greater in tap water than in finished water and source water. In general, the levels of bacteria were higher in source water than in tap water, and the levels of ARB were higher in tap water than in finished water, indicating that there was regrowth of bacteria in drinking water distribution systems. Elevated resistance to some antibiotics was observed during water treatment and in tap water. Water treatment might increase the antibiotic resistance of surviving bacteria, and water distribution systems may serve as an important reservoir for the spread of antibiotic resistance to opportunistic pathogens.

Mercury pollution from the past mining of gold and silver in the Americas

The development of the patio amalgamation process into an industrial scale operation in 1554 stimulated the massive production of silver in the New World but left behind an unprecedented quantity of mercury pollution. The annual loss of mercury in the silver mines of Spanish America averaged 612 tonnes/year (range 292-1085 tonnes/year) between 1580 and 1900. The production and importation of mercury into the United States ranged from 268 to 2820 tonnes/year and averaged - 1360 tonnes/year between 1850 and 1900. Approximately 90% of the mercury consumed in the United States during this period was employed in gold and silver extraction. The cumulative losses of mercury to the environment due to the production of precious metals in the Americas totalled - 257 400 tonnes, with 196 000 tonnes dispersed in South and Central America and 61 380 tonnes in the United States. Approximately 60-65% of the mercury lost is believed to have been released to the atmosphere, suggesting that gold and silver mines were a dominant source of atmospheric mercury pollution. Because of its high volatility, any deposited mercury can readily be re-emitted to the atmosphere. The continuing recycling of this large mass of mercury may partly be responsible for the high fluxes of mercury in many parts of North and South America and the high background levels of mercury in the global environment.