for the Lancet NCDI Poverty Commission Study Group Executive summary"As we embark on this great collective journey, we pledge that no one will be left behind. Recognizing that the dignity of the human person is fundamental, we wish to see the goals and targets met for all nations and peoples and for all segments of society. And we will endeavour to reach the furthest behind first."Transforming our world: the 2030 agenda for sustainable development 1

In this paper, the unique real-time measurement capabilities of aerosol time-of-flight mass spectrometry (ATOFMS) for characterizing atmospheric aerosol particles are demonstrated. ATOFMS is used to obtain the aerodynamic size and chemical composition of individual aerosol particles sampled directly into the instrument from outdoors. Such measurements are made in-situ by combining a unique dual-laser aerodynamic particle sizing system to size and track individual particles through the instrument and laser desorption/ionization time-of-flight mass spectrometry to obtain correlated single particle composition data. At typical ambient concentrations, the size and chemical composition of 50−100 particles per minute can be measured (up to 600 per minute at high particle concentrations). Presented here for the first time are compositionally resolved particle size distributions of ambient aerosol particles, showing definitive size/composition correlations. A goal of these studies is to ultimately couple data obtained from the dynamic monitoring of individual particles in atmospheric systems with that obtained using conventional ambient aerosol sampling to assist in sorting out complex field data on atmospheric processes.

The chemical composition and size of individual particles derived from combustion products of several species found in Southern California were obtained using aerosol timeof-flight mass spectrometry. The major inorganic species observed in >90% of all biomass burning particles is potassium, indicated by the atomic ion, as well as clusters containing chloride, nitrate, and sulfate ions in the mass spectra. By obtaining positive and negative ion mass spectra it is possible to identify distinct chemical marker combinations in particles resulting from the burning of plant species, which in turn allows for differentiation from particles produced from other combustion sources such as vehicle emissions. Using these markers, particles derived from biomass burning were identified in ambient aerosol samples.

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Real‐time single particle mass spectrometry, or continuous aerosol mass spectrometry, was originally developed in the 1970s for the purpose of identifying the chemical composition of airborne particulate matter in real‐time. Although this technique has continued to evolve throughout the following decades, the fundamental characteristic of this method remains the same, involving the continuous introduction of solid particle or liquid droplets directly into the ion source region of a mass spectrometer. Continuous sample introduction allows for the chemical analysis of single airborne particles in real‐time. A number of mass analyzers have been employed in real‐time single particle mass spectrometry. The original real‐time single particle mass spectrometer used a magnetic sector mass analyzer. Quadrupole, double‐focusing, and ion trap mass spectrometers have also been utilized. The majority of the current real‐time single particle mass spectrometry techniques use time‐of‐flight mass spectrometry. In the literature, a variety of general names have been applied to real‐time single particle mass spectrometry methods. These names include direct‐inlet mass spectrometry, on‐line laser microprobe mass spectrometry, particle analysis by mass spectrometry, particle beam mass spectrometry, and rapid‐single particle mass spectrometry. This review covers real‐time single particle mass spectrometry techniques that were developed from 1973 through 1998, specifically for analyzing airborne particulate matter, including environmental aerosols, biological aerosols, and clean‐room aerosols. Because the majority of the historical and current real‐time single particle mass spectrometers have been employed for atmospheric aerosols, this topic is the primary focus of this review. This review does not include on‐line mass spectrometry methods that are employed as a detector for other instrumental methods, such as liquid chromatography. © 2000 John Wiley & Sons, Inc., Mass Spec Rev 19: 248–274, 2000