A timeline of hydrogen sulfide (H2S) research: From environmental toxin to biological mediator.

The history of H2S - as an environmental toxin - dates back to 1700, to the observations of the Italian physician Bernardino Ramazzini, whose book "De Morbis Artificum Diatriba" described the painful eye irritation and inflammation of "sewer gas" in sewer workers. The gas has subsequently been identified as hydrogen sulfide (H2S), and opened three centuries of research into the biological roles of H2S. The current article highlights the key discoveries in the field of H2S research, including (a) the toxicological studies, which characterized H2S as an environmental toxin, and identified some of its modes of action, including the inhibition of mitochondrial respiration; (b) work in the field of bacteriology, which, starting in the early 1900s, identified H2S as a bacterial product - with subsequently defined roles in the regulation of periodontal disease (oral bacterial flora), intestinal epithelial cell function (enteral bacterial flora) as well as in the regulation of bacterial resistance to antibiotics; and (c), work in diverse fields of mammalian biology, which, starting in the 1940s, identified H2S as an endogenous mammalian enzymatic product, the functions of which - among others, in the cardiovascular and nervous system - have become subjects of intensive investigation for the last decade. The current review not only enumerates the key discoveries related to H2S made over the last three centuries, but also compiles the most frequently cited papers in the field which have been published over the last decade and highlights some of the current 'hot topics' in the field of H2S biology.

Organophosphorus Compounds at 80: Some Old and New Issues.

One of the major classes of pesticides is that of the organophosphates (OPs). Initial developments date back almost 2 centuries but it was only in the mid-1940s that OPs reached a prominent status as insecticides, a status that, albeit declining, is still ongoing. OPs are highly toxic to nontarget species including humans, the primary effects being an acute cholinergic toxicity (responsible for thousands of poisoning each year) and a delayed polyneuropathy. Several issues of current debate and investigation on the toxicology of OPs are discussed in this brief review. These include (1) possible additional targets of OPs, (2) OPs as developmental neurotoxicants, (3) OPs and neurodegenerative diseases, (4) OPs and the "aerotoxic syndrome," (5) OPs and the microbiome, and (6) OPs and cancer. Some of these issues have been debated and studied for some time, while others are newer, suggesting that the study of the toxicology of OPs will remain an important scientific and public health issue for years to come.

Historical intake and elimination of polychlorinated biphenyls and organochlorine pesticides by the Australian population reconstructed from biomonitoring data.

Quantifying the competing rates of intake and elimination of persistent organic pollutants (POPs) in the human body is necessary to understand the levels and trends of POPs at a population level. In this paper we reconstruct the historical intake and elimination of ten polychlorinated biphenyls (PCBs) and five organochlorine pesticides (OCPs) from Australian biomonitoring data by fitting a population-level pharmacokinetic (PK) model. Our analysis exploits two sets of cross-sectional biomonitoring data for PCBs and OCPs in pooled blood serum samples from the Australian population that were collected in 2003 and 2009. The modeled adult reference intakes in 1975 for PCB congeners ranged from 0.89 to 24.5ng/kgbw/day, lower than the daily intakes of OCPs ranging from 73 to 970ng/kgbw/day. Modeled intake rates are declining with half-times from 1.1 to 1.3years for PCB congeners and 0.83 to 0.97years for OCPs. The shortest modeled intrinsic human elimination half-life among the compounds studied here is 6.4years for hexachlorobenzene, and the longest is 30years for PCB-74. Our results indicate that it is feasible to reconstruct intakes and to estimate intrinsic human elimination half-lives using the population-level PK model and biomonitoring data only. Our modeled intrinsic human elimination half-lives are in good agreement with values from a similar study carried out for the population of the United Kingdom, and are generally longer than reported values from other industrialized countries in the Northern Hemisphere.

Environmental pollution and allergy: historical aspects.

It may be a coincidence, but it is a fact that the first clear characterization of hay fever began in England where modern industrialization started in Europe. Only at the end of the 20th century were associations of the increasing prevalence of allergy with outdoor air pollution discussed. The seminal study came from Japan from the group of T. Miyamoto linking the increase in Japanese cedar pollinosis to an increased prevalence of Diesel cars and probably exposure to Diesel exhaust in epidemiological, animal experimental and in vitro studies. In Germany first epidemiological studies were done in North Rhine-Westphalia and Bavaria in 1987 and 1988 showing a striking prevalence of allergic disease of up to 10-20% in preschool children. After German reunification the most surprising observation was a lower prevalence of hay fever in East German children compared to the West, although there was a much higher air pollution with SO2 and large particulate matter. Modern smog as found over West German cities most likely originating from traffic exhaust and consisting of fine and ultrafine particles was shown to be associated with higher incidence rates of allergy and allergic sensitization. In the 10 years after reunification there was a steep increase of allergy prevalence in East German children reaching almost the same level as in West Germany. Obviously, a multitude of lifestyle factors - beyond air pollution - may be involved in the explanation of this phenomenon. Surprisingly the skin manifestation of atopy, namely atopic eczema, was more frequent in East German children compared to the West, thus differing from airway allergy. Meanwhile in vitro studies and animal experiments have shown that a variety of air pollutants mostly from environmental tobacco smoke (indoors) and from traffic exhaust (outdoors) can stimulate immune cells inducing a Th2-dominated response besides their irritative effects. While 50 years ago in allergy textbooks a clear distinction was made between 'toxic' or 'allergic', the newly developed concept of allergotoxicology has stimulated research tremendously, meaning 'the investigation of effects of toxic substances upon the induction, elicitation and maintenance of allergic reactions'.

Relationship between polycyclic aromatic hydrocarbons (PAHs) and particle size in dated core sediments in Lake Lianhuan, Northeast China.

Atmospheric particle associated with pyrogenic polycyclic aromatic hydrocarbons (PAHs) poses serious threats to human health by inhalation exposure, especially in semiarid areas. Hence, the distributions of PAHs and particle size in two core sediments collected from Lake Lianhuan, Northeast China were studied. The sediments were dated radiometrically, and particle size distribution and PAH concentration were evaluated and potential human health risk was assessed. From 1980 to 2007, the dominant PAHs in the two cores were 2- and 3-ring PAHs, and the concentrations of 3-6 ring PAHs gradually increased from the early 1990s. Diagnostic ratios indicated that pyrogenic PAHs were the main sources of PAHs which changed over time from combustions of wood and coal to liquid fossil fuel sources. Fine particles (<65 µm) were the predominant particle size (56-97%). Lacustrine source (with the peak towards 200-400 µm) and eolian sources derived from short (2.0-10 and 30-65 µm) and long (0.4-1.0 µm) distance suspension were indentified from frequency distribution pattern of particle size. Significant correlations between 3-6 ring PAHs (especially carcinogenic 5-6 ring PAHs) and 10-35 µm particulate fractions indicated that eolian particles played an important role in adsorbing pyrogenic PAHs. Petroleum source of PAHs was only identified during the 1980s in one core sediments, in which positive correlations between 2-ring PAHs and particulate fractions of >125 µm were found. Future research should focus on the seven carcinogenic pyrogenic PAHs due to a rapidly increasing trend since 1995 based on the assessment of toxic equivalency factors.

[Mustard gas bombs found astray in the Faxaflói bay. Mustard gas: usage and poisonings]. / Sinnepsgassprengjur á afvegum í Faxaflóa. Sinnepsgas: notkun thess og eitranir.

The finding in 1972 of two World War II mustard gas artillery shells in crushed shell sediment dredged in the Faxaflói Bay and transported as raw material for cement production at Akranes (Western Iceland) is reported. One of the shells was wedged in a stone crusher in the raw material processing line and was ruptured. As a result dark fluid with a garlic like smell seeped out from the metal canister. The attending employees believed the metal object to be inert and tried to cut it out with a blow torch. This resulted in the explosion of the shell charge and in the exposure of four employees to mustard gas. All suffered burns on their hands and two of them in the eyes also. The second shell was detonated in the open at a distance from the factory. Emphasis is given to the fact that instant, or at least as soon as possible, cleansing and washing is the most efficient measure to be taken against the debilitating effects of mustard gas. It is also pointed out that the active principle in mustard gas (dichlorodiethyl sulphide) can easily be synthesized and none of the precursor substances are subjected to any restrictions of use. The authors conclude that mustard gas bombs may still be found in the arsenals of some military powers in spite of an international convention that prohibits the production, stockpiling and the use of chemical weapons. Terrorist groups have also seemingly tried to aquire mustard gas bombs and other chemical weapons. Therefore cases of mustard gas poisoning might still occur.

Historical perspectives on cadmium toxicology.

The first health effects of cadmium (Cd) were reported already in 1858. Respiratory and gastrointestinal symptoms occurred among persons using Cd-containing polishing agent. The first experimental toxicological studies are from 1919. Bone effects and proteinuria in humans were reported in the 1940's. After World War II, a bone disease with fractures and severe pain, the itai-itai disease, a form of Cd-induced renal osteomalacia, was identified in Japan. Subsequently, the toxicokinetics and toxicodynamics of Cd were described including its binding to the protein metallothionein. International warnings of health risks from Cd-pollution were issued in the 1970's. Reproductive and carcinogenic effects were studied at an early stage, but a quantitative assessment of these effects in humans is still subject to considerable uncertainty. The World Health Organization in its International Program on Chemical Safety, WHO/IPCS (1992) (Cadmium. Environmental Health Criteria Document 134, IPCS. WHO, Geneva, 1-280.) identified renal dysfunction as the critical effect and a crude quantitative evaluation was presented. In the 1990's and 2000 several epidemiological studies have reported adverse health effects, sometimes at low environmental exposures to Cd, in population groups in Japan, China, Europe and USA (reviewed in other contributions to the present volume). The early identification of an important role of metallothionein in cadmium toxicology formed the basis for recent studies using biomarkers of susceptibility to development of Cd-related renal dysfunction such as gene expression of metallothionein in peripheral lymphocytes and autoantibodies against metallothionein in blood plasma. Findings in these studies indicate that very low exposure levels to cadmium may give rise to renal dysfunction among sensitive subgroups of human populations such as persons with diabetes.

Slightly weathered Exxon Valdez oil persists in Gulf of Alaska beach sediments after 16 years.

Oil stranded by the 1989 Exxon Valdez spill has persisted in subsurface sediments of exposed shores for 16 years. With annualized loss rates declining from approximately 68% yr(-1) prior to 1992 to approximately 4% yr(-1) after 2001, weathering processes are retarded in both sediments and residual emulsified oil ("oil mousse"), and retention of toxic polycyclic aromatic hydrocarbons is prolonged. The n-alkanes, typically very readily oxidized by microbes, instead remain abundant in many stranded emulsified oil samplesfrom the Gulf of Alaska. They are less abundant in Prince William Sound samples, where stranded oil was less viscous. Our results indicate that, at some locations, remaining subsurface oil may persist for decades with little change.

Retrospective time-trend study of polybrominated diphenyl ether and polybrominated and polychlorinated biphenyl levels in human serum from the United States.

Six polybrominated diphenyl ethers (PBDEs), one hexabromobiphenyl [polybrominated biphenyl (PBB)], and one hexachlorobiphenyl [polychlorinated biphenyl (PCB)] were measured in 40 human serum pools collected in the southeastern United States during 1985 through 2002 and in Seattle, Washington, for 1999 through 2002. The concentrations of most of the PBDEs, which are commercially used as flame retardants in common household and commercial applications, had significant positive correlations with time of sample collection, showing that the concentrations of these compounds are increasing in serum collected in the United States. In contrast, PCB and PBB levels were negatively correlated with sample collection year, indicating that the levels of these compounds have been decreasing since their phaseout in the 1970s.

Response of three paleo-primary production proxy measures to development of an urban estuary.

In this study we present a novel comparison of three proxy indicators of paleoproductivity, pigments, biogenic silica (BSi), and cysts of autotrophic dinoflagellates measured in cored sediments from New Bedford Harbor, Massachusetts. In addition to detailed historical reports we use palynological signals of land clearance, changes in the ratio of centric and pennate diatoms, sedimentary organic carbon and stable carbon isotopes to constrain our interpretations. Our study spans the period from prior to European settlement to approximately 1977, during which watersheds were cleared, port development occurred and much of the coastal property became industrialized. The combined effects of nutrient loading from watershed clearance and urban sewage on the estuarine ecosystem shifted not only levels of primary production, but also the nature of the production. Our proxies show that when European colonists first arrived the estuarine production was benthic-dominated, but eventually became pelagic-dominated. Importance of water column production (by diatoms and dinoflagellates) rapidly increased as soil nitrogen was released following forest clearance. Stabilization in rates of forest clearance is reflected as a decline in production. However, population increases in the urbanizing watershed brought new sources of nutrients through direct sewage discharge, apparently again stimulating primary production. We assume that early 20th century changes in sewage discharge and introduction of heavy metals into Harbor waters caused a temporary reduction in primary production. The introduction of a new sewer outfall near the core site and changes in estuarine hydrography due to construction of a hurricane barrier across the mouth of the harbor are reflected by renewed water column production, but decreases in the population of diatoms and dinoflagellates. Fossil pigments suggest renewed water column production in the latest years recorded by our sediment core.

Origin of lead in eight Central European peat bogs determined from isotope ratios, strengths, and operation times of regional pollution sources.

Lead originating from coal burning, gasoline burning, and ore smelting was identified in 210Pb-dated profiles through eight peat bogs distributed over an area of 60,000 km2. The Sphagnum-dominated bogs were located mainly in mountainous regions of the Czech Republic bordering with Germany, Austria, and Poland. Basal peat 14C-dated at 11,000 years BP had a relatively high 206Pb/207Pb ratio (1.193). Peat deposited around 1800 AD had a lower 206Pb/207Pb ratio of 1.168-1.178, indicating that environmental lead in Central Europe had been largely affected by human activity (smelting) even before the beginning of the Industrial Revolution. Five of the sites exhibited a nearly constant 206Pb/207Pb ratio (1.175) throughout the 19th century, resembling the "anthropogenic baseline" described in Northern Europe (1.17). At all sites, the 206Pb/207Pb ratio of peat decreased at least until 1980; at four sites, a reversal to more radiogenic values (higher 206Pb/207Pb), typical of easing pollution, was observed in the following decade (1980-1990). A time series of annual outputs for 14 different mining districts dispersing lead into the environment has been constructed for the past 200 years. The production of Ag-Pb, coal, and leaded gasoline peaked in 1900, 1980, and 1980, respectively. In contrast to other European countries, no peak in annual Pb accumulation rates was found in 1900, the year of maximum ore smelting. The highest annual Pb accumulation rates in peat were consistent with the highest Pb emission rates from coal-fired power plants and traffic (1980). Although maximum coal and gasoline production coincided in time, their isotope ratios were unique. The mean measured 206Pb/207Pb ratios of local coal, ores, and gasoline were 1.19, 1.16, and 1.11, respectively. A considerable proportion of coal emissions, relative to gasoline emisions, was responsible for the higher 206Pb/207Pb ratios in the recent atmosphere (1.15) compared to Western Europe (1.10). As in West European countries, the gasoline sold in the Czech Republic during the Communist era (1948-1989) contained an admixture of low-radiogenic Precambrian lead from Australia.

The dynamic performances of DDTs in the environment and Japanese exposure to them: a historical perspective after the ban.

The fugacity model for evaluating DDTs dynamic performances in the environment was combined with the dietary exposure evaluation model, including the contribution of imported food, to develop the macroscopic mathematical model relating DDTs in the environment with the health risks of the reference Japanese. The model validity was examined by comparing the simulated DDTs concentrations in environmental media, various kinds of food, and dietary intake with those observed. Numerical simulations were done for the past half and future of one century to evaluate the effect of the DDTs usage prohibition in 1970 in Japan. The major results obtained under the limits considered are as follows. The DDTs concentrations in environmental media, various kinds of foods, and the dietary intake showed the steady exponential decrease after the DDTs usage prohibition in 1970. The DDE/DDTs ratio is larger in the higher position in an ecological system, and increased steadily with time. The critical exposure of DDTs occurred through animal product intake until 1960; after 1990 marine product intake caused the most exposure. The estimated DDTs intake was evaluated to be less than the PTDI and RfD. The annual excess cancer induction risk due to the annual dietary intake of DDTs was the largest at the level of (0.5 - 2.0) x 10(-6) (1/yr) in the early 1970s. The effect of the DDT usage prohibition on dietary exposure reduction was expected to appear after about 20 years. The life-span excess cancer induction risk was conservatively estimated to be larger than 10(-5) (1/lifespan) for the reference Japanese who were born before 1970. The DDTs usage prohibition in 1970 was effective to reduce the life-span cancer risk under the 10(-5) level.

Gas-phase polychlorinated biphenyl and hexachlorocyclohexane concentrations near the Great Lakes: a historical perspective.

The Integrated Atmospheric Deposition Network (IADN) has been measuring gas-phase, polychlorinated biphenyl (PCB) concentrations at sites near Lakes Michigan and Superior for over a decade. Data through 2000 were used in this study to investigate PCB temporal trends in the Great Lakes atmosphere. Decreasing trends were found at both sites, and half-lives of approximately 20 yr were calculated using IADN data. However, when these data were supplemented by historical data for Lakes Michigan and Superior dating back to 1977, half-lives dropped to 10 and 6 yr, respectively. These latter half-lives agreed well with half-lives in other environmental compartments. Exponential curves fitted to the historical and IADN data indicated little decline in PCB concentrations in the basin since the mid-1990s. A similar historical analysis of alpha-and gamma-hexachlorocyclohexane (HCH) data indicated that IADN data were the best predictor of trends, resulting in half-lives of around 4 yr for both compounds. Gamma-HCH concentrations, however, have shown little decline in recent years, most likely because of its continuing use. PCB and alpha-HCH temporal trends indicated that bans on these substances have helped to remove them from the atmosphere. This work also showed that decades of data may be necessary to properly interpret long-term temporal trends in gas-phase organochlorine concentrations.

[The outer environment--now and then]. / Det ytre miljø--før og nå.

Hazardous environmental factors in Norway have changed considerably over the last decades, often for the better. During the last five-year period, water-works serving 800,000 Norwegians have been renovated. The earlier high levels of sulphur dioxide and lead in urban air are now very low, whereas suspended particulate matter and nitrogen oxides continue to be at levels which can induce adverse health effects. Radon and tobacco smoke are now important indoor contaminants. Moisture-induced damage in dwellings may lead to health problems; the extent of such damage is, however, not known. A number of fjords are still contaminated with metals, PAH (polycyclic aromatic hydrocarbons), PCB (polychlorinated biphenyls) and dioxins, even though industrial discharge to water and air has been greatly reduced. Body burdens of DDT, PCB and dioxins have been markedly lowered over time. There is a continuous increase in the use of chemicals, though the chemicals are better tested and controlled than before. The total volume of pesticides used has fallen over the last three decades. There are no clear changes over the last 15 to 20 years in perceived noise exposure.