Comparative short-term health responses to sulfur dioxide exposure and other common stresses in a panel of asthmatics

Construction of a novel near-infrared fluorescent probe with multiple fluorescence emission and its application for SO2 derivative detection in cells and living zebrafish

Sulfur dioxide (SO₂) in biological systems is an important gaseous signal molecule and plays important roles in physiological activities. It can be endogenously produced by enzymes in mitochondria during oxidation of sulphur-containing molecules. Thus, the development of probes for sulfur dioxide detection in biological environment is necessary. Here, a new near-infrared fluorescent probe (Rh-TPA) with multiple fluorescence emission was constructed and applied for SO₂ derivative detection. Rh-TPA was constructed via conjugation of a rhodamine analogue with a triphenylamine group. Rh-TPA exhibited a major emission peak at 740 nm and a shoulder peak at 810 nm. After interacting with SO₂ derivatives, the conjugated system dissociated into two smaller chromophores with two emission peaks (520 nm and 570 nm) in the visible region. The probe showed negligible cytotoxicity, as demonstrated by the MTT results. Biological imaging application experiments indicated that the probe can be used to image SO₂ derivatives in HeLa cells and living zebrafish.

Chemical characteristics of haze particles in Xi'an during Chinese Spring Festival: Impact of fireworks burning

Fireworks burning releases massive fine particles and gaseous pollutants, significantly deteriorating air quality during Chinese Lunar New Year (LNY) period. To investigate the impact of the fireworks burning on the atmospheric aerosol chemistry, 1-hr time resolution of PM_2.5 samples in Xi'an during the winter of 2016 including the LNY were collected and detected for inorganic ions, acidity and liquid water content (LWC) of the fine aerosols. PM_2.5 during the LNY was 167±87μg/m³, two times higher than the China National Ambient Air Quality Standard (75μg/m³). K⁺ (28wt.% of the total ion mass) was the most abundant ion in the LNY period, followed by SO₄^2- (25wt.%) and Cl^- (18wt.%). In contrast, NO₃^- (34wt.%) was the most abundant species in the haze periods (hourly PM_2.5>75μg/m³), followed by SO₄^2- (29.2wt.%) and NH₄⁺ (16.3wt.%), while SO₄^{2 -} (35wt.%) was the most abundant species in the clean periods (hourly PM_2.5<75μg/m³), followed by NO₃^- (23.1wt.%) and NH₄⁺ (11wt.%). Being different from the acidic nature in the non-LNY periods, aerosol in the LNY period presented an alkaline nature with a pH value of 7.8±1.3. LWC during the LNY period showed a robust linear correlation with K₂SO₄ and KCl, suggesting that aerosol hygroscopicity was dominated by inorganic salts derived from fireworks burning. Analysis of correlations between the ratios of NO₃^-/SO₄^2- and NH₄⁺/SO₄^2- indicated that heterogeneous reaction of HNO₃ with NH₃ was an important formation pathway of particulate nitrate and ammonium during the LNY period.

Evaluation of the experimental basis for assessment factors to protect individuals with asthma from health effects during short-term exposure to airborne chemicals

BACKGROUND

Asthmatic individuals constitute a large sub-population that is often considered particularly susceptible to the deleterious effects of inhalation of airborne chemicals. However, for most such chemicals information on asthmatics is lacking and inter-individual assessment factors (AFs) of 3-25 have been proposed for use in the derivation of health-based guideline values.

OBJECTIVE

To evaluate available information in attempt to determine whether a general difference in airway response during short-term exposure between healthy and asthmatic individuals can be identified, and whether current AFs for inter-individual variability provide sufficient protection for asthmatics.

METHODS

After performing systematic review of relevant documents and the scientific literature estimated differential response factors (EDRF) were derived as the ratio between the lowest observed adverse effect levels for healthy and asthmatic subjects based on studies in which both groups were tested under the same conditions. Thereafter, the concentration-response relationships for healthy and asthmatic subjects exposed separately to four extensively tested chemicals (nitrogen dioxide, ozone, sulfuric acid, sulfur dioxide) were compared on the basis of combined data. Finally, a Benchmark Concentration (BMC) analysis was performed for sulfur dioxide.

RESULTS

We found evidence of higher sensitivity among asthmatics (EDRF > 1) to 8 of 19 tested chemicals, and to 3 of 11 mixtures. Thereafter, we confirmed the higher sensitivity of asthmatics to sulfuric acid and sulfur dioxide. No difference was observed in the case of ozone and nitrogen dioxide. Finally, our BMC analysis of sulfur dioxide indicated a ninefold higher sensitivity among asthmatics.

CONCLUSION

Although experimental data are often inconclusive, our analyses suggest that an AF of 10 is adequate to protect asthmatics from the deleterious respiratory effects of airborne chemicals.

Do group responses mask the effects of air pollutants on potentially sensitive individuals in controlled human exposure studies?

To establish primary National Ambient Air Quality Standards (NAAQS) for criteria air pollutants such as nitrogen dioxide (NO2), ozone (O3), and sulfur dioxide (SO2), US EPA relies in part on controlled human exposure studies. It has been suggested that evaluating average responses for all participants in these studies may not reflect the responses of sensitive participants in these studies. To evaluate this, we identified controlled exposure studies with multiple exposure concentrations or durations that provided individual-level lung function data. Based on individual lung function responses at specific exposure concentrations and the slope of individual concentration-response curves, we identified 12 participants out of a total of 208 participants in 12 studies who were potentially sensitive to O3, SO2, or sulfuric acid (H2SO4). We did not identify any participants sensitive to NO2. All of these participants were found to be potentially sensitive only at concentrations that were well above the NAAQS (SO2), above likely ambient concentrations (H2SO4), or at concentrations at which the study reported significant lung function effects for all participants (O3). Based on our analysis, average responses for all participants combined adequately reflect lung function responses for potentially sensitive study participants at concentrations in the range of the current NAAQS.

Analysis of the concentration-respiratory response among asthmatics following controlled short-term exposures to sulfur dioxide

Some of the most compelling evidence of sulfur dioxide (SO(2))-induced respiratory morbidity is derived from a large body of studies involving controlled short-term exposures among groups of asthmatic volunteers. These studies were extensively cited in the recently completed review of the primary National Ambient Air Quality Standards for SO(2). Although it is clear from these investigations that exposure to SO(2) may result in a significant increase in bronchoconstriction, there is uncertainty regarding the range of concentrations over which this respiratory response occurs. The objective of this study was to better characterize the concentration-response relationship between SO(2) and measures of bronchoconstriction using individual subject lung function response data. In reviewing studies of asthmatics exposed to SO(2) during 5- to 10-min periods of elevated ventilation, we observed clear and consistent evidence of an increase in the bronchoconstrictive response to SO(2) with increasing exposure concentrations between 0.2 and 1.0 ppm. In a subsequent analysis of individual subject data, it was found that those asthmatics experiencing SO(2)-induced respiratory effects at relatively high exposure concentrations are also more likely than nonresponders to experience similar effects after exposure to lower SO(2) concentrations (≤0.4 ppm). Although the clinical significance of these effects is unsettled, the findings provide additional support to epidemiologic evidence of an association between ambient SO(2) concentration and various measures of respiratory morbidity in the general population.

A review of controlled human SO₂ exposure studies contributing to the US EPA integrated science assessment for sulfur oxides

Laboratory studies involving intentional and highly controlled exposures to air pollutants among groups of human volunteers provide valuable information related to the potential health effects of pollutants regulated under the US Clean Air Act. These controlled human exposure studies often provide biological plausibility for the associations between air-pollutant concentration and a given health endpoint observed in epidemiologic investigations. In some cases, results from human laboratory studies provide evidence of a relevant health effect at ambient or near-ambient concentrations and thus directly support the selection of air quality standard levels. In the recently completed review of the US National Ambient Air Quality Standards (NAAQS) for sulfur dioxide (SO₂), the US Environmental Protection Agency (EPA) concluded that short-term exposures to SO₂ are causally associated with an increase in respiratory morbidity. This determination was based in large part on findings from laboratory studies of controlled exposures to SO₂ among small groups of asthmatic individuals. The purpose of this review is to concisely present an overview of the evidence from controlled human exposure studies of SO₂-induced respiratory health effects following short-term exposures. While the majority of these studies were conducted over 20 years ago, the findings and insights gained from this work continues to play an integral role in evaluating the respiratory effects of ambient exposures to SO₂.

Study of temporal variation in ambient air quality during Diwali festival in India

The variation in air quality was assessed from the ambient concentrations of various air pollutants [total suspended particle (TSP), particulate matter < or =10 microm (PM(10)), SO(2), and NO(2)] for pre-Diwali, Diwali festival, post-Diwali, and foggy day (October, November, and December), Delhi (India), from 2002 to 2007. The extensive use of fireworks was found to be related to short-term variation in air quality. During the festival, TSP is almost of the same order as compared to the concentration at an industrial site in Delhi in all the years. However, the concentrations of PM(10), SO(2), and NO(2) increased two to six times during the Diwali period when compared to the data reported for an industrial site. Similar trend was observed when the concentrations of pollutants were compared with values obtained for a typical foggy day each year in December. The levels of these pollutants observed during Diwali were found to be higher due to adverse meteorological conditions, i.e., decrease in 24 h average mixing height, temperature, and wind speed. The trend analysis shows that TSP, PM(10), NO(2), and SO(2) concentration increased just before Diwali and reached to a maximum concentration on the day of the festival. The values gradually decreased after the festival. On Diwali day, 24-h values for TSP and PM(10) in all the years from 2002 to 2007 and for NO(2) in 2004 and 2007 were found to be higher than prescribed limits of National Ambient Air Quality Standards and exceptionally high (3.6 times) for PM(10) in 2007. These results indicate that fireworks during the Diwali festival affected the ambient air quality adversely due to emission and accumulation of TSP, PM(10), SO(2), and NO(2).

Sulfur-related air pollutants induce the generation of platelet-activating factor, 5-lipoxygenase- and cyclooxygenase-products in canine alveolar macrophages via activation of phospholipases A2

Recent studies have shown that long-term in vivo exposure of dogs to neutral sulfur(IV)/sulfite aerosols induces mild inflammatory reactions, whereas the combination of neutral sulfite with acidic sulfur(VI)/sulfate aerosols evokes less pronounced effects. To understand underlying mechanisms, we studied in vitro the role of lipid mediators in the responses of alveolar macrophages (AMs) to sulfur-related compounds under neutral (pH 7) or moderate acidic (pH 6) conditions. Canine AMs incubated with sulfite at pH 7 released threefold higher amounts of platelet-activating factor than control (P < 0.005). Generation of arachidonic acid, leukotriene B4, 5-hydroxy-eicosatetraenoic acid, prostaglandin E2, thromboxane B2 and 12-hydroxyheptadecatrienoic acid increased twofold (P < 0.0005). However, these metabolites remained unchanged following incubation of AMs with sulfite at pH 6 or with sulfate at pH 7 or pH 6. Mediator release by sulfite-treated AMs at pH 7 stimulated respiratory burst activity of neutrophils. Inhibition of MAPK pathway by PD 98059, of cytosolic (cPLA2) and secretory phospholipases A2 by AACOCF3 and thioetheramide-PC, respectively, reduced sulfite-induced eicosanoid formation in AMs. Sulfite activated cPLA2 activity twofold at pH 7. This mechanism of sulfite-stimulated responses in phospholipid metabolism predicts that chronic exposure to sulfur(IV)/sulfite is associated with a considerable health risk.

Sulfur: its clinical and toxicologic aspects

Although there is no known dietary requirement for inorganic sulfur, it is an essential element for all animal species in as much as they all require the sulfur-containing amino acid methionine. There are three predominate forms of organic sulfur in animals and humans: 1). the thiomethyl of methionine residues in protein; 2). the sulfhydryl disulfides of protein; and 3). the compounds containing ester or amide bound sulfates of glycosaminoglycans, steroids, and many xenobiotic metabolites. Thus, sulfur becomes an important constituent of amino acids, proteins, enzymes, vitamins and other biomolecules. Unlike mammalian species, plants can use inorganic sulfur and synthesize methionine from which are synthesized all the other important sulfur compounds. Hence, sulfur deficiency occurs mainly when plants are grown in sulfur-depleted soils and when humans and animals consume low-protein diets. In recent times, however, the increasing prevalence of refining petroleum and smelting sulfur compounds of metallic minerals into free metals are having a large impact on the balance of sulfur in the environment. Sulfur toxicity is associated mainly with high levels of the element and its toxic volatile substances in the environment. Sulfur dioxide (SO(2)), a major air pollutant, may adversely affect animal and human health by causing bronchitis, bronchoconstriction, and increased pulmonary resistance.

Fatal and near-fatal asthma in children exposed to fireworks

BACKGROUND

Fireworks accounted for an estimated 8,300 emergency department visits during 1997 in the United States. Firecrackers, bottle rockets, roman candles, and sparklers contribute to the most hospitalizations. Burns account for the majority of these injuries Fireworks are manufactured from a variety of chemicals, which include the known irritant, sulfur dioxide, as one of the products of combustion. We are reporting one fatal and one near fatal asthma exacerbation after use of fireworks.

OBJECTIVE

We are reporting two patients who had severe asthma exacerbation shortly after having exposure to different types of fireworks.

METHODS

Patient data were collected from patients that presented the week of July 4, 1998 to our institution. Information was also obtained from the Consumer Product Safety Commission and the National Weather Service.

RESULT

The patients presented to our institution within hours of their exposure from the fireworks. One patient had a respiratory arrest and was resuscitated, but subsequently expire. The second patient was able to treated aggressively and avoided intubation.

CONCLUSIONS

These cases demonstrate risks that fireworks may present to the asthmatic child and that patient's with asthma should exercise caution when observing or participating in fireworks demonstrations.