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

Serum calcium and magnesium levels and quality of life in environmentally exposed populations in Kazakhstan

The relationship between the levels of essential elements and various aspects of well-being in environmentally exposed populations still needs to be better understood. The present study aims to investigate the potential connections between serum concentrations of calcium (Ca), magnesium (Mg), and quality of life (QoL) in environmentally exposed populations in Kazakhstan. The present study involved 1881 nominally healthy individuals aged 18-52 years who were permanent residents of Abay, Borodulikha, Ust-Kamenogorsk, Kurchum, Uralsk, Aksay, and Berezovka settlements. These settlements were selected to represent different types of environmental exposure: radioactive fallout from the Semipalatinsk Nuclear Test Site (SNTS), non-ferrous metallurgy, and the condensate gas field, compared to environmentally unexposed territories. The Russian version of the SF-36 questionnaire was used to assess the participants' quality of life. Serum Ca levels were measured using colorimetry with O-cresolphthalein, and serum Mg concentrations were measured using colorimetry with xylidyl blue. Both elevated and decreased serum Ca levels were more frequently observed in the environmentally exposed populations. The prevalence of hypermagnesemia was highest among residents near the condensate gas field. Environmentally exposed populations residing near the SNTS and in Ust-Kamenogorsk exhibited lower scores in some QoL domains. In contrast, people near the condensate gas field showed comparable or even higher QoL scores than the control population. Only serum Mg demonstrated a significant association with the average QoL scores, while Ca did not show such an association. These findings have important implications for public health interventions.

The Scientific Basis for Occupational Exposure Limits for Hydrogen Sulphide-A Critical Commentary

OBJECTIVES

Occupational exposure limits for hydrogen sulphide (H₂S) vary considerably; three expert group reports, published from 2006 to 2010, each recommend different limits. Some jurisdictions are considering substantial reductions.

METHODS

This review assesses the scientific evidence used in these recommendations and presents a new systematic review of human studies from 2006-20, identifying 33 studies.

RESULTS

The three major reports all give most weight to two sets of studies: of physiological effects in human volunteers, and of effects in the nasal passages of rats and mice. The human studies were done in one laboratory over 20 years ago and give inconsistent results. The breathing style and nasal anatomy of rats and mice would make them more sensitive than humans to inhaled agents. Each expert group applied different uncertainly factors. From these reports and the further literature review, no clear evidence of detrimental health effects from chronic occupational exposures specific to H₂S was found. Detailed studies of individuals in communities with natural sources in New Zealand have shown no detrimental effects. Studies in Iceland and Italy show some associations; these and various other small studies need verification.

CONCLUSIONS

The scientific justification for lowering occupational exposure limits is very limited. There is no clear evidence, based on currently available studies, that lower limits will protect the health of workers further than will the current exposure limits used in most countries. Further review and assessment of relevant evidence is justified before exposure limits are set.

Graphitic carbon nitride quantum dots as an "off-on" fluorescent switch for determination of mercury(II) and sulfide

A rapid method has been developed for the determination of Hg(II) and sulfide by using graphitic carbon nitride quantum dots (g-CNQDs) as a fluorescent probe. The interaction between Hg(II) and g-CNQDs leads to the quenching of the blue g-CNQD fluorescence (with excitation/emission peaks at 390/450 nm). However, the fluorescence can be recovered after addition of sulfide such that the "turn-off" state is switched back to the "turn-on" state. The g-CNQDs were fully characterized by transmission electron microscopy, X-ray diffractometry, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, UV-vis absorption and fluorescence spectroscopy. Under the optimal experimental conditions, this probe is highly selective and sensitive to Hg(II). The linear response to Hg(II) extends from 0.20 to 21 μM with a detection limit of 3.3 nM. In addition, sulfide can be detected via the recovery of fluorescence. The linear response range for sulfide species is from 8.0 to 45 μM with a detection limit of 22 nM. The mechanism of the "turn-off-on" scheme is discussed. The methods have been applied to the analysis of spiked tap water, lake water and wastewater samples. Graphical abstract Schematic of an off-on fluorescent probe for mercury(II). The fluorescence of graphitic carbon nitride quantum dots (g-CNQDs) is quenched by Hg²⁺ but is recovered after reacting with S^2- as it can combine with Hg²⁺ on the surface of g-CNQDs.