Vertical distribution and temporal evolution of formaldehyde and glyoxal derived from MAX-DOAS observations: The indicative role of VOC sources

The association between long-term exposure to ambient formaldehyde and respiratory mortality risk: A national study in China

INTRODUCTION

While ambient formaldehyde (HCHO) concentrations are increasing worldwide, there was limited research on its health effects.

OBJECTIVES

To assess the association of long-term exposure to ambient HCHO with the risk of respiratory (RESP) mortality and the associated mortality burden in China.

METHODS

Annual and seasonal RESP death and tropospheric HCHO vertical columns data were collected in 466 counties/districts across China during 2013-2016. A difference-in-differences approach combined with a generalized linear mixed-effects regression model was employed to assess the exposure-response association between long-term ambient HCHO exposure and RESP mortality risk. Additionally, we computed the attributable fraction (AF) to gauge the proportion of RESP mortality attributable to HCHO exposure.

RESULTS

This analysis encompassed 560,929 RESP deaths. The annual mean ambient HCHO concentration across selected counties/districts was 8.02×1015 ± 2.22×1015 molec.cm-2 during 2013-2016. Each 1.00×1015 molec.cm-2 increase in ambient HCHO was associated with a 1.61 % increase [excess risk (ER), 95 % confidence interval (CI): 1.20 %, 2.03 %] in the RESP mortality risk. The AF of RESP mortality attributable to HCHO was 12.16 % (95 %CI:9.33 %, 14.88 %), resulting in an annual average of 125,422 (95 %CI:96,404, 153,410) attributable deaths in China. Stratified analyses suggested stronger associations in individuals aged ≥65 years old (ER=1.87 %, 95 %CI:1.43 %, 2.32 %), in cold seasons (ER=1.00 %, 95 %CI:0.56 %, 1.44 %), in urban areas (ER=1.65 %, 95 %CI:1.15 %, 2.16 %), and in chronic obstructive pulmonary disease patients (ER=1.95 %, 95 %CI:1.42 %, 2.48 %).

CONCLUSIONS

This study suggested that long-term HCHO exposure may significantly increase the risk of RESP mortality, leading to a substantial mortality burden. Targeted measures should be implemented to control ambient HCHO pollution promptly.

Broadband Cavity-Enhanced Absorption Spectroscopy (BBCEAS) Coupled with an Interferometer for On-Band and Off-Band Detection of Glyoxal

Glyoxal (CHOCHO) is a trace gas in the atmosphere, often used as an indicator of biogenic emissions. It is frequently compared to formaldehyde concentrations, which serve as indicators of anthropogenic emissions, to gain insights into the characteristics of the environmental source. This study employed broadband cavity-enhanced absorption spectroscopy to detect gaseous CHOCHO, methylglyoxal, and NO2. Two different detection methods are compared. Spectrograph and CCD Detection: This approach involves coupling the system to a spectrograph with a charge-coupled device (CCD) detector. It achieved a 1 min 1-σ detection limit of 2.5 × 108 molecules/cm3, or 10 parts per trillion (ppt). Methylglyoxal and NO2 achieved 1 min 1-σ detection limits of 34 ppt and 22 ppt, respectively. Interferometer and PMT Detection: In this method, an interferometer is used in conjunction with a photomultiplier tube (PMT) detector. It resulted in a 2 min 1-σ detection limit of 1.5 × 1010 molecules/cm3, or 600 ppt. The NO2 2 min 1-σ detection limit was determined to be 900 ppt. Concentrations of methylglyoxal were difficult to determine using this method, as they appeared to be below the detection limit of the instrument. This study discusses the advantages and limitations of each of these detection methods.

Phytoremediation of indoor formaldehyde by plants and plant material

Formaldehyde evolves from various household items and is of environmental and public health concern. Removal of this contaminant from the indoor air is of utmost importance and currently, various practices are in the field. Among these practices, indoor plants are of particular importance because they help in controlling indoor temperature, moisture, and oxygen concentration. Plants and plant materials studied for the purpose have been reviewed hereunder. The main topics of the review are, mechanism of phytoremediation, plants and their benefits, plant material in formaldehyde remediation, and airtight environmental and health issues. Future research in the field is also highlighted which will help new researches to plan for the remediation of formaldehyde in indoor air. The remediation capacity of several plants has been tabulated and compared, which gives easy access to assess various plants for remediation of the target pollutant. Challenges and issues in the phytoremediation of formaldehyde are also discussed.Novelty statement: Phytoremediation is a well-known technique to mitigate various organic and inorganic pollutants. The technique has been used by various researchers for maintaining indoor air quality but its efficiency under real-world conditions and human activities is still a question and is vastly affected relative to laboratory conditions. Several modifications in the field are in progress, here in this review article we have summarized and highlighted new directions in the field which could be a better solution to the problem in the future.