Cobinamide is effective for treatment of hydrogen sulfide-induced neurological sequelae in a mouse model

Hydrogen sulfide (H2 S) is a highly neurotoxic gas. Acute exposure can lead to neurological sequelae among survivors. A drug for treating neurological sequelae in survivors of acute H2 S intoxication is needed. Using a novel mouse model we evaluated the efficacy of cobinamide (Cob) for increasing survival of, and reducing neurological sequalae in, mice exposed to sublethal doses of H2 S. There were two objectives: (1) to determine the dose-response efficacy of Cob and (2) to determine the effective therapeutic time window of Cob. To explore objective 1, mice were injected intramuscularly with Cob at 0, 50, or 100 mg/kg at 2 min after H2 S exposure. For objective 2, mice were injected intramuscularly with 100 mg/kg Cob at 2, 15, and 30 min after H2 S exposure. For both objectives, mice were exposed to 765 ppm of H2 S gas. Cob significantly reduced H2 S-induced lethality in a dose-dependent manner (P < 0.05). Cob-treated mice exhibited significantly fewer seizures and knockdowns compared with the H2 S-exposed group. Cob also reversed H2 S-induced weight loss, behavioral deficits, neurochemical changes, cytochrome c oxidase enzyme inhibition, and neurodegeneration in a dose- and time-dependent manner (P < 0.01). Overall, these findings show that Cob increases survival and is neuroprotective in a mouse model of H2 S-induced neurological sequelae.

Hydrogen Sulfide Specifically Alters NAD(P)H Quinone Dehydrogenase 1 (NQO1) Olfactory Neurons in the Rat

The regions of the olfactory epithelium affected by hydrogen sulfide (H₂S) toxicity in the rat present a striking similarity with the developmental olfactory zone 1 described in the mouse. This zone which is the only region containing neurons expressing NAD(P)H quinone dehydrogenase 1 (NQO1) is involved in complex behavioral responses in rodents, and other mammals, triggered by specific olfactory stimuli. We therefore sought to determine whether (1) olfactory neurons expressing NQO1 are located in the same regions in the rats and in the mice and (2) there is an overlap between olfactory neurons expressing this protein and those affected by the toxicity of H₂S. Rats were exposed to H₂S - 200 ppm during 3 h, three consecutive days- and displayed symmetric acute segmental necrosis of the neurons and sustentacular cells of the olfactory epithelium in the dorsomedial nasal cavity. We found that expression of NQO1 in Sprague-Dawley rats spatially recapitulated that of the mouse. The degree of agreement or overlap between these two populations of neurons (necrosis vs. NQO1 expression) reached 80.2%. Although the underlying mechanisms accounted for the high sensitivity for NQO1 neurons -or the relative protection of non NQO1 neurons- to sulfide toxicity remain to be established, this observation is offering an intriguing approach that could be used to acutely suppress the pool of neural cells in olfactory zone I and to understand the mechanisms of toxicity and protection of other populations of neurons exposed to sulfide.

Chronic Obstructive Pulmonary Disease in Farmers: A Systematic Review

OBJECTIVE

Chronic obstructive pulmonary disease (COPD) is a significant public health problem but it is unclear whether agricultural work causes an increased risk of disease. The aim of this review was to study COPD risk among farmers and analyze occupational exposures in agricultural workplaces.

METHODS

A systematic literature search was conducted to identify epidemiological studies investigating COPD prevalence in farmers.

RESULTS

In the 14 studies reviewed, COPD prevalence ranged from 3% to 68% due to different characteristics of study population, working activities, case definition/diagnosis. Livestock farmers were at higher risk and significant associations were observed for exposure to organic dusts, endotoxins, mites, ammonia, and hydrogen sulfide.

CONCLUSIONS

Farming work was associated with greater risk of developing COPD. However, considering the several variables that may influence the disease prevalence in farmers, we suggest the adoption of a standardized research strategy.

Human health cost of hydrogen sulfide air pollution from an oil and gas Field

Introduction and objective. The Karachaganak oil and gas condensate field (KOGCF), one of the largest in the world, located in the Republic of Kazakhstan (RoK) in Central Asia, is surrounded by 10 settlements with a total population of 9,000 people. Approximately73% of this population constantly mention a specific odour of rotten eggs in the air, typical for hydrogen sulfide (H₂S) emissions, and the occurrence of low-level concentrations of hydrogen sulfide around certain industrial installations (esp. oil refineries) is a well known fact. Therefore, this study aimed at determining the impact on human health and the economic damage to the country due to H₂S emissions. Materials and method. Dose-response dependency between H₂S concentrations in the air and cardiovascular morbidity using multiple regression analysis was applied. Economic damage from morbidity was derived with a newly-developed method, with Kazakhstani peculiarities taken into account. Results.Hydrogen sulfide air pollution due to the KOGCF activity costs the state almost $60,000 per year. Moreover, this is the reason for a more than 40% rise incardiovascular morbidity in the region. Conclusion. The reduction of hydrogen sulfide emissions into the air is recommended, as well as successive constant ambient air monitoring in future. Economic damage evaluation should be made mandatory, on a legal basis, whenever an industrial facility operation results in associated air pollution.

Roles of the Exogenous H2S-Mediated SR-A Signaling Pathway in Renal Ischemia/ Reperfusion Injury in Regulating Endoplasmic Reticulum Stress-Induced Autophagy in a Rat Model

OBJECTIVE

This study aims to explore the effects of the exogenous hydrogen sulfide (H2S)-mediated scavenger receptor A (SR-A) signaling pathway on renal ischemia/reperfusion injury (IRI) by regulating endoplasmic reticulum (ER) stress-induced autophagy in rats.

METHODS

A total of 48 normal Sprague-Dawley (SD) rats and SR-A knockout rats were selected and divided into six groups (n = 8): wild-type (WT) + sham, WT + ischemia-reperfusion (I/R), WT + I/R + NaHS, SR-A-/- + sham, SR-A-/- + I/R and SR-A-/- + I/R + NaHS. The concentrations of urinary protein, blood urea nitrogen (BUN), serum creatinine (SCR), malondialdehyde (MDA) and H2S in renal tissue were detected. qRT-PCR and Western blotting were used to detect the mRNA and protein levels of IL-6, TGF-β, SR-A, LC3I, LC3II, P62, PERK, ATF6 and IRE1 pathway-related genes. A TUNEL assay was used to detect cell apoptosis. Electron microscopy was applied to observe the structure of renal autophagosomes.

RESULTS

Compared with the WT + sham group, in the rates of the WT + I/R group, the urine volume, urinary protein, BUN, SCR and MDA concentrations, the mRNA and protein expression of IL-6, TGF-β, LC3II/I, and ER stress pathway-related genes, the cell apoptosis index, and the number of autophagosomes were significantly increased 24 h after I/R, while P62 and SR-A protein expression and SOD and H2S concentrations were significantly decreased (all P < 0.05). The levels of renal injury, autophagy and ER stress pathway-related genes were decreased in the WT + I/R + NaHS group but were increased in the SR-A-/- + I/R group relative to the WT + I/R group. No significant differences were observed in the urine volume; the concentrations of urinary protein, BUN, SCR and MDA; the SOD activity; the mRNA and protein expression of IL-6, TGF-β, SR-A, GRP78, SR-A, GPR94, ATF4, IRE1, XBP1, ATF6, and eIF2α; the cell apoptosis index; or the number of autophagosomes in rats of the SR-A-/- + I/R and SR-A-/- + I/R + NaHS groups (all P > 0.05).

CONCLUSION

These results demonstrate that the exogenous H2S-mediated SR-A signaling pathway reduces renal IRI injury by up-regulating ER stress-induced autophagy in rats.

Hazards after the storm: Floodwater drainage pump stations and exposure to hydrogen sulfide

A hurricane can present unique hazards that exist long after the strong winds and heavy rains have subsided. These hazards may not only be physical, but chemical as well. Hydrogen sulfide (H₂S) represents an important and potentially overlooked hazard that can be naturally produced in floodwaters following a hurricane. In August of 2012, in the wake of Hurricane Isaac, Plaquemines Parish, Louisiana was submerged under a blanket of floodwater. To remove floodwaters that had breached the levee system designed to keep water out, temporary drainage pump stations were installed at strategic locations. The transfer of floodwaters at these drainage stations resulted in the generation of elevated concentrations of airborne H₂S at the pumping stations. The generation of H₂S at these pumping stations represented a potential inhalation hazard for workers; thus, awareness for possible H₂S exposure at these installments is crucial.

Involvement of water channel Aquaporin 5 in H2S-induced pulmonary edema

Acute exposure to hydrogen sulfide (H₂S) poses a significant threat to life, and the lung is one of the primary target organs of H₂S. However, the mechanisms involved in H₂S-induced acute pulmonary edema are poorly understood. This study aims to investigate the effects of H₂S on the expression of water channel aquaporin 5 (AQP5) and to elucidate the signaling pathways involved in AQP5 regulation. In an in vivo study, C57BL6 mice were exposed to sub-lethal concentrations of inhaled H₂S, and histological injury of the lungs and ultrastructure injury of the epithelial cells were evaluated. With real-time PCR and western blot assays, we found that H₂S exposure contributed to a significant decrease in AQP5 expression both in murine lung tissue and the A549 cell line, and the ERK1/2 and p38 MAPK signaling pathways were demonstrated to be implicated in AQP5 regulation. Therefore, adjusting AQP5 protein levels could be considered a therapeutic strategy for the treatment of APE induced by H₂S and other hazardous gases.

Acute hydrogen sulfide-induced neuropathology and neurological sequelae: challenges for translational neuroprotective research

Hydrogen sulfide (H2 S), the gas with the odor of rotten eggs, was formally discovered in 1777, over 239 years ago. For many years, it was considered an environmental pollutant and a health concern only in occupational settings. Recently, however, it was discovered that H2 S is produced endogenously and plays critical physiological roles as a gasotransmitter. Although at low physiological concentrations it is physiologically beneficial, exposure to high concentrations of H2 S is known to cause brain damage, leading to neurodegeneration and long-term neurological sequelae or death. Neurological sequelae include motor, behavioral, and cognitive deficits, which are incapacitating. Currently, there are concerns about accidental or malicious acute mass civilian exposure to H2 S. There is a major unmet need for an ideal neuroprotective treatment, for use in the field, in the event of mass civilian exposure to high H2 S concentrations. This review focuses on the neuropathology of high acute H2 S exposure, knowledge gaps, and the challenges associated with development of effective neuroprotective therapy to counteract H2 S-induced neurodegeneration.

Is exogenous hydrogen sulfide a relevant tool to address physiological questions on hydrogen sulfide?

This review challenges the use of solutions of dissolved exogenous H2S in the literature as a tool to determine the potential physiological functions of endogenous H2S as well as its putative therapeutic applications. Our major point of contention is that solutions of dissolved H2S are used in vitro at concentrations, within the high microM range, which are above the concentrations of dissolved H2S found in blood and tissues during lethal H2S exposure in vivo. In addition, since the levels of toxicity are extremely variable among cell types, a property that is seldom acknowledged, the physiological relevance of data obtained after local or in-vitro administrations of H2S at concentrations of few microM is far from certain. Conversely, the rate of disappearance of the dissolved pool of H2S in the body (being trapped or oxidized), which we found to be at least of several micromoles/kg/min, is so rapid in vivo that if relatively low quantities of H2S, i.e. few micromoles for instance, are administered, no change in H2S concentrations in the body is to be expected, unless toxic levels are used. Protocols looking at the effects of compounds slowly releasing H2S must also resolve a similar conundrum, as their effects must be reconciled with the unique ability of the blood and tissues to get rid of H2S and the steepness of the dose-toxic effects relationship. Only by developing a comprehensive framework in which H2S metabolism and toxicity will be used as a rationale to justify any experimental approach will we be able to bring definitive evidence supporting a protective role for exogenous H2S, if any, and its putative function as an endogenous mediator.

Direct and indirect effects of petroleum production activities on the western fence lizard (Sceloporus occidentalis) as a surrogate for the dunes sagebrush lizard (Sceloporus arenicolus)

The dunes sagebrush lizard (Sceloporus arenicolus) is a habitat specialist of conservation concern limited to shin oak sand dune systems of New Mexico and Texas (USA). Because much of the dunes sagebrush lizard's habitat occurs in areas of high oil and gas production, there may be direct and indirect effects of these activities. The congeneric Western fence lizard (Sceloporus occidentalis) was used as a surrogate species to determine direct effects of 2 contaminants associated with oil and gas drilling activities in the Permian Basin (NM and TX, USA): herbicide formulations (Krovar and Quest) and hydrogen sulfide gas (H2S). Lizards were exposed to 2 concentrations of H2 S (30 ppm or 90 ppm) and herbicide formulations (1× or 2× label application rate) representing high-end exposure scenarios. Sublethal behavioral endpoints were evaluated, including sprint speed and time to prey detection and capture. Neither H2S nor herbicide formulations caused significant behavioral effects compared to controls. To understand potential indirect effects of oil and gas drilling on the prey base, terrestrial invertebrate biomass and order diversity were quantified at impacted sites to compare with nonimpacted sites. A significant decrease in biomass was found at impacted sites, but no significant effects on diversity. The results suggest little risk from direct toxic effects, but the potential for indirect effects should be further explored.

Upregulation of spinal NMDA receptors mediates hydrogen sulfide-induced hyperalgesia

Hydrogen sulfide (H2S) is an endogenous neurotransmitter that importantly regulates various physiological and pathological events including pain signal transduction. In this study, we investigated the role of spinal NMDA receptors in the nociception induced by intraplantar injection of NaHS, an H2S donor. Intraplantar injection of NaHS into hindpaw significantly decreased the paw withdrawal threshold (PWT) in contralateral hindpaw. However, intraplantar formalin injection did not produce PWT in contralateral hindpaw. Intrathecal injection of methemoglobin, a H2S scavenger, abolished hyperalgesia induced by NaHS. In addition, NaHS-induced hyperalgesia was partly, but significantly, attenuated by intrathecal injection of hydroxylamine, a cystathionine-β-synthase (CBS) inhibitor. RT-PCR and western blotting analysis revealed that NR2B mRNA and protein levels were increased in the spinal dorsal horn, but not in dorsal root ganglion (DRG) in rats subjected to NaHS intraplantar injection. Collectively, these data suggest that peripheral injection of H2S donor causes hyperalgesia through increase in NR2B expression and production of H2S in the spinal cord.

Effect of environmental exposure to hydrogen sulfide on central nervous system and respiratory function: a systematic review of human studies

BACKGROUND

Assessment of the health effects of low-level exposure to hydrogen sulfide (H2S) on humans through experiments, industrial, and community studies has shown inconsistent results.

OBJECTIVE

To critically appraise available studies investigating the effect of H2S on the central nervous system (CNS) and on respiratory function.

METHODS

A search was conducted in 16 databases for articles published between January 1980 and July 2014. Two researchers independently evaluated potentially relevant papers based on a set of inclusion/exclusion criteria.

RESULTS

Twenty-seven articles met the inclusion criteria: 6 experimental, 12 industry-based studies, and 10 community-based studies (one article included both experimental and industry-based studies). The results of the systematic review varied by study setting and quality. Several community-based studies reported associations between day-to-day variations in H2S levels and health outcomes among patients with chronic respiratory conditions. However, evidence from the largest and better-designed community-based studies did not support that chronic, ambient H2S exposure has health effects on the CNS or respiratory function. Results from industry-based studies varied, reflecting the diversity of settings and the broad range of H2S exposures. Most studies did not have individual measurements of H2S exposure.

DISCUSSION

The results across studies were inconsistent, justifying the need for further research.

An Anticancer Role of Hydrogen Sulfide in Human Gastric Cancer Cells

Hydrogen sulfide (H2S) can be synthesized in mammalian cells by cystathionine γ-lyase (CSE) and/or cystathionine β-synthase (CBS). Both CSE and CBS are expressed in rat gastric tissues but their role in human gastric neoplasia has been unclear. The aims of the present study were to detect CSE and CBS proteins in human gastric cancer and determine the effect of exogenous NaHS on the proliferation of gastric cancer cells. We found that both CSE and CBS proteins were expressed in human gastric cancer cells and upregulated in human gastric carcinoma mucosa compared with those in noncancerous gastric samples. NaHS induced apoptosis of gastric cancer cells by regulating apoptosis related proteins. Also, NaHS inhibited cancer cell migration and invasion. An antigastric cancer role of H2S is thus indicated.

Oxic microshield and local pH enhancement protects Zostera muelleri from sediment derived hydrogen sulphide

Seagrass is constantly challenged with transporting sufficient O₂ from above- to belowground tissue via aerenchyma in order to maintain aerobic metabolism and provide protection against phytotoxins. Electrochemical microsensors were used in combination with a custom-made experimental chamber to analyse the belowground biogeochemical microenvironment of Zostera muelleri under changing environmental conditions. Measurements revealed high radial O₂ release of up to 500 nmol O2 cm(-2) h(-1) from the base of the leaf sheath, maintaining a c. 300-μm-wide plant-mediated oxic microzone and thus protecting the vital meristematic regions of the rhizome from reduced phytotoxic metabolites such as hydrogen sulphide (H₂S). H₂S intrusion was prevented through passive diffusion of O₂ to belowground tissue from leaf photosynthesis in light, as well as from the surrounding water column into the flow-exposed plant parts during darkness. Under water column hypoxia, high belowground H₂S concentrations at the tissue surface correlated with the inability to sustain the protecting oxic microshield around the meristematic regions of the rhizome. We also found increased pH levels in the immediate rhizosphere of Z. muelleri, which may contribute to further detoxification of H₂S through shifts in the chemical speciation of sulphide. Zostera muelleri can modify the geochemical conditions in its immediate rhizosphere, thereby reducing its exposure to H₂S.

Hydrogen sulfide intoxication

Hydrogen sulfide (H2S) is a hazard primarily in the oil and gas industry, agriculture, sewage and animal waste handling, construction (asphalt operations and disturbing marshy terrain), and other settings where organic material decomposes under reducing conditions, and in geothermal operations. It is an insoluble gas, heavier than air, with a very low odor threshold and high toxicity, driven by concentration more than duration of exposure. Toxicity presents in a unique, reliable, and characteristic toxidrome consisting, in ascending order of exposure, of mucosal irritation, especially of the eye ("gas eye"), olfactory paralysis (not to be confused with olfactory fatigue), sudden but reversible loss of consciousness ("knockdown"), pulmonary edema (with an unusually favorable prognosis), and death (probably with apnea contributing). The risk of chronic neurcognitive changes is controversial, with the best evidence at high exposure levels and after knockdowns, which are frequently accompanied by head injury or oxygen deprivation. Treatment cannot be initiated promptly in the prehospital phase, and currently rests primarily on supportive care, hyperbaric oxygen, and nitrite administration. The mechanism of action for sublethal neurotoxicity and knockdown is clearly not inhibition of cytochrome oxidase c, as generally assumed, although this may play a role in overwhelming exposures. High levels of endogenous sulfide are found in the brain, presumably relating to the function of hydrogen sulfide as a gaseous neurotransmitter and immunomodulator. Prevention requires control of exposure and rigorous training to stop doomed rescue attempts attempted without self-contained breathing apparatus, especially in confined spaces, and in sudden release in the oil and gas sector, which result in multiple avoidable deaths.

Effects of conventional and hydrogen sulfide-releasing non-steroidal anti-inflammatory drugs in rats with stress-induced and epinephrine-induced gastric damage

Mechanisms of gastric defence under conditions of combined influence of acute stress and non-steroidal anti-inflammatory drugs (NSAIDs) are still poorly studied. The aim of this study was to explore the effects of different types of NSAIDs (naproxen, celecoxib and ATB-346) in producing experimental gastric lesions (induced by water-restraint stress (WRS) or by epinephrine (EPN) injection) and to determine the role of lipid peroxidation and the nitric oxide (NO) system in the pathogenesis of the damage. Male rats were used (eight per group) in this work. The NSAIDs were all administered at a dose 10 mg kg(-1) 30 min prior to WRS or EPN injection. Administration of naproxen to the control rats caused development of gastric lesions, whereas administration of a hydrogen sulfide (H2S)-releasing NSAID (ATB-346) or a selective cyclooxygenase-2 inhibitor (celecoxib) did not cause gastric damage. In contrast, lipid peroxidation processes were enhanced in all groups as was the activity of NO synthase (NOS). Pretreatment with naproxen in the WRS model caused an increase in severity of damage and a decrease in NOS activity. ATB-346 displayed beneficial effects, manifested by a decrease in the area of gastric damage, but parameters of lipid peroxidation and the NOS system did not differ substantially from those in the group treated with naproxen. Administration of different NSAIDs under conditions of EPN-induced gastric damage resulted in the decrease in NOS activity and lipid peroxidation. None of the tested NSAIDs exacerbated EPN-induced gastric mucosal injury; indeed, they all reduced the extent of damage.

H2S exposure elicits differential expression of candidate genes in fish adapted to sulfidic and non-sulfidic environments

Disentangling the effects of plasticity, genetic variation, and their interactions on organismal responses to environmental stressors is a key objective in ecological physiology. We quantified the expression of five candidate genes in response to hydrogen sulfide (H2S) exposure in fish (Poecilia mexicana, Poeciliidae) from a naturally sulfide-rich environment as well as an ancestral, non-sulfidic population to test for constitutive and environmentally dependent population differences in gene expression patterns. Common garden raised individuals that had never encountered environmental H2S during their lifetime were subjected to short or long term H2S exposure treatments or respective non-sulfidic controls. The expression of genes involved in responses to H2S toxicity (cytochrome c oxidase, vascular endothelial growth factor, and cytochrome P450-2J6), H2S detoxification (sulfide:quinone oxidoreductase), and endogenous H2S production (cystathionine γ lyase) was determined in both gill and liver tissues by real time PCR. The results indicated complex changes in expression patterns that--depending on the gene--not only differed between organs and populations, but also on the type of H2S exposure. Populations differences, both constitutive and H2S exposure dependent (i.e., plastic), in gene expression were particularly evident for sulfide:quinone oxidoreductase, vascular endothelial growth factor, and to a lesser degree for cytochrome P450-2J6. Our study uncovered putatively adaptive modifications in gene regulation that parallel previously documented adaptive changes in phenotypic traits.

Chronic ambient hydrogen sulfide exposure and cognitive function

BACKGROUND

Exposures to hydrogen sulfide gas (H2S) have been inconclusively linked to a variety of negative cognitive outcomes. We investigated possible effects on cognitive function in an urban population with chronic, low-level exposure to H2S.

METHODS

Participants were 1637 adults, aged 18-65 years from Rotorua city, New Zealand, exposed to ambient H2S from geothermal sources. Exposures at homes and workplaces were estimated from data collected by summer and winter H2S monitoring networks across Rotorua in 2010/11. Metrics for H2S exposure at the time of participation and for exposure over the last 30 years were calculated. H2S exposure was modeled both as continuous variables and as quartiles of exposure covering the range of 0-64 ppb (0-88 μg/m(3)). Outcomes were neuropsychological tests measuring visual and verbal episodic memory, attention, fine motor skills, psychomotor speed and mood. Associations between cognition and measures of H2S exposure were investigated with multiple regression, while covarying demographics and factors known to be associated with cognitive performance.

RESULTS

The consistent finding was of no association between H2S exposure and cognition. Quartiles of H2S exposure had a small association with simple reaction time: higher exposures were associated with faster response times. Similarly, for digit symbol, higher H2S exposures tended to be marginally associated with better performance.

CONCLUSION

The results provide evidence that chronic H2S exposure, at the ambient levels found in and around Rotorua, is not associated with impairment of cognitive function.

Association of air pollution and use of glyceryl trinitrate against angina pectoris: a population-based case-crossover study

BACKGROUND

Ambient air pollution has been associated with increased cardiovascular morbidity and mortality. In Reykjavik, Iceland, air pollutant concentrations exceed official health limits several times every year. The aim was to study the association of concentrations of NO2, O3, PM10, and H2S in the Reykjavik capital area with the dispensing of anti-angina pectoris medication, glyceryl trinitrate to the inhabitants.

METHODS

Data on daily dispensing of glyceryl trinitrate, were retrieved from the Icelandic Medicines Registry. Data on hourly concentrations of NO2, O3, PM10, and H2S were obtained from the Environment Agency of Iceland. A case-crossover design was used, based on the dispensing of glyceryl trinitrate to 5,246 individuals (≥18 years) between 2005 and 2009.

RESULTS

For every 10 μg/m3 increase of NO2 and O3 3-day mean concentrations, the odds ratio (OR) for daily dispensing of glyceryl trinitrates was 1.136 (95% confidence intervals (CI) 1.069-1.207) and 1.094 (95% CI 1.029-1.163) at lag 0, and OR was 1.096 (95% CI 1.029-1.168) and 1.094 (95% CI 1.028-1.166) at lag 1, respectively.

CONCLUSIONS

These findings suggest that NO2 and O3 ambient air concentrations may adversely affect cardiovascular health, as measured by the dispensing of glyceryl trinitrates for angina pectoris. Further, the findings suggest that data on the dispensing of medication may be a valuable health indicator when studying the effect of air pollution on cardiovascular morbidity.

Exposure to toxic waste containing high concentrations of hydrogen sulphide illegally dumped in Abidjan, Côte d'Ivoire

INTRODUCTION

On August 2006, a cargo ship illegally dumped 500 t of toxic waste containing high concentrations of hydrogen sulphide in numerous sites across Abidjan. Thousands of people became ill. Seventeen deaths were associated with toxic waste exposure.

MATERIALS AND METHODS

This study reports on environmental and health problems associated with the incident. A cross-sectional transect study was conducted in five waste dumping site areas.

RESULTS

Of the households, 62.1% (n = 502) were exposed to the effects of the pollutants and 51.1% of the interviewed people (n = 2,368) in these households showed signs of poisoning. Most important symptoms were cough (37.1%), asthenia (33.1%), pruritus (29.9%) and nausea (29.1%).

DISCUSSION

The health effects showed different frequencies in the five waste impact sites. Among the poisoned persons, 21.1% (n = 532) presented symptoms on the survey day (i.e., 4 months after incident). Transect sampling allowed to determine a radius of vulnerability to exposure of up to 3 km from the point of toxic waste disposal.

CONCLUSION

The area of higher vulnerability is influenced by various environmental factors, such as size and severity of pollution site, duration of toxic waste pollution on the impact site and locally climatic conditions. The surveillance of effects on environment and human health is warranted to monitor the development.

Mitochondrial adaptations to utilize hydrogen sulfide for energy and signaling

Sulfur is a versatile molecule with oxidation states ranging from -2 to +6. From the beginning, sulfur has been inexorably entwined with the evolution of organisms. Reduced sulfur, prevalent in the prebiotic Earth and supplied from interstellar sources, was an integral component of early life as it could provide energy through oxidization, even in a weakly oxidizing environment, and it spontaneously reacted with iron to form iron-sulfur clusters that became the earliest biological catalysts and structural components of cells. The ability to cycle sulfur between reduced and oxidized states may have been key in the great endosymbiotic event that incorporated a sulfide-oxidizing α-protobacteria into a host sulfide-reducing Archea, resulting in the eukaryotic cell. As eukaryotes slowly adapted from a sulfidic and anoxic (euxinic) world to one that was highly oxidizing, numerous mechanisms developed to deal with increasing oxidants; namely, oxygen, and decreasing sulfide. Because there is rarely any reduced sulfur in the present-day environment, sulfur was historically ignored by biologists, except for an occasional report of sulfide toxicity. Twenty-five years ago, it became evident that the organisms in sulfide-rich environments could synthesize ATP from sulfide, 10 years later came the realization that animals might use sulfide as a signaling molecule, and only within the last 4 years did it become apparent that even mammals could derive energy from sulfide generated in the gastrointestinal tract. It has also become evident that, even in the present-day oxic environment, cells can exploit the redox chemistry of sulfide, most notably as a physiological transducer of oxygen availability. This review will examine how the legacy of sulfide metabolism has shaped natural selection and how some of these ancient biochemical pathways are still employed by modern-day eukaryotes.

Hydrogen sulfide and particle matter levels associated with increased dispensing of anti-asthma drugs in Iceland's capital

BACKGROUND

Air pollutants in Iceland's capital area include hydrogen sulfide (H2S) emissions from geothermal power plants, particle pollution (PM10) and traffic-related pollutants. Respiratory health effects of exposure to PM and traffic pollutants are well documented, yet this is one of the first studies to investigate short-term health effects of ambient H2S exposure.

OBJECTIVES

The aim of this study was to investigate the associations between daily ambient levels of H2S, PM10, nitrogen dioxide (NO2) and ozone (O3), and the use of drugs for obstructive pulmonary diseases in adults in Iceland's capital area.

METHODS

The study period was 8 March 2006 to 31 December 2009. We used log-linear Poisson generalized additive regression models with cubic splines to estimate relative risks of individually dispensed drugs by air pollution levels. A three-day moving average of the exposure variables gave the best fit to the data. Final models included significant covariates adjusting for climate and influenza epidemics, as well as time-dependent variables.

RESULTS

The three-day moving average of H2S and PM10 levels were positively associated with the number of individuals who were dispensed drugs at lag 3-5, corresponding to a 2.0% (95% confidence interval [CI] 0.4, 3.6) and 0.9% (95% CI 0.1, 1.8) per 10 μg/m3 pollutant concentration increase, respectively.

CONCLUSION

Our findings indicated that intermittent increases in levels of particle matter from traffic and natural sources and ambient H2S levels were weakly associated with increased dispensing of drugs for obstructive pulmonary disease in Iceland's capital area. These weak associations could be confounded by unevaluated variables hence further studies are needed.

Inner ear morphology in the Atlantic molly Poecilia mexicana--first detailed microanatomical study of the inner ear of a cyprinodontiform species

BACKGROUND

Fishes show an amazing diversity in hearing abilities, inner ear structures, and otolith morphology. Inner ear morphology, however, has not yet been investigated in detail in any member of the diverse order Cyprinodontiformes. We, therefore, studied the inner ear of the cyprinodontiform freshwater fish Poecilia mexicana by analyzing the position of otoliths in situ, investigating the 3D structure of sensory epithelia, and examining the orientation patterns of ciliary bundles of the sensory hair cells, while combining μ-CT analyses, scanning electron microscopy, and immunocytochemical methods. P. mexicana occurs in different ecotypes, enabling us to study the intra-specific variability (on a qualitative basis) of fish from regular surface streams, and the Cueva del Azufre, a sulfidic cave in southern Mexico.

RESULTS

The inner ear of Poecilia mexicana displays a combination of several remarkable features. The utricle is connected rostrally instead of dorso-rostrally to the saccule, and the macula sacculi, therefore, is very close to the utricle. Moreover, the macula sacculi possesses dorsal and ventral bulges. The two studied ecotypes of P. mexicana showed variation mainly in the shape and curvature of the macula lagenae, in the curvature of the macula sacculi, and in the thickness of the otolithic membrane.

CONCLUSIONS

Our study for the first time provides detailed insights into the auditory periphery of a cyprinodontiform inner ear and thus serves a basis--especially with regard to the application of 3D techniques--for further research on structure-function relationships of inner ears within the species-rich order Cyprinodontiformes. We suggest that other poeciliid taxa, or even other non-poeciliid cyprinodontiforms, may display similar inner ear morphologies as described here.

Relation between malodor, ambient hydrogen sulfide, and health in a community bordering a landfill

BACKGROUND

Municipal solid waste landfills are sources of air pollution that may affect the health and quality of life of neighboring communities.

OBJECTIVES

To investigate health and quality of life concerns of neighbors related to landfill air pollution.

METHODS

Landfill neighbors were enrolled and kept twice-daily diaries for 14d about odor intensity, alteration of daily activities, mood states, and irritant and other physical symptoms between January and November 2009. Concurrently, hydrogen sulfide (H(2)S) air measurements were recorded every 15-min. Relationships between H(2)S, odor, and health outcomes were evaluated using conditional fixed effects regression models.

RESULTS

Twenty-three participants enrolled and completed 878 twice-daily diary entries. H(2)S measurements were recorded over a period of 80d and 1-h average H(2)S=0.22ppb (SD=0.27; range: 0-2.30ppb). Landfill odor increased 0.63 points (on 5-point Likert-type scale) for every 1ppb increase in hourly average H(2)S when the wind was blowing from the landfill towards the community (95% confidence interval (CI): 0.29, 0.91). Odor was strongly associated with reports of alteration of daily activities (odds ratio (OR)=9.0; 95% CI: 3.5, 23.5), negative mood states (OR=5.2; 95% CI: 2.8, 9.6), mucosal irritation (OR=3.7; 95% CI=2.0, 7.1) and upper respiratory symptoms (OR=3.9; 95% CI: 2.2, 7.0), but not positive mood states (OR=0.6; 95% CI: 0.2, 1.5) and gastrointestinal (GI) symptoms (OR=1.0; 95% CI: 0.4, 2.6).

CONCLUSIONS

Results suggest air pollutants from a regional landfill negatively impact the health and quality of life of neighbors.