Graduate & postdoctoral positions

Positions are available for motivated doctoral students and postdoctoral fellows with outstanding preparation.

Doctoral students in our group undertake field measurements, analyze large datasets, and build statistical mathematical models to better understand and mitigate human exposures to air pollution and their health effects.

A background in environmental science or engineering — especially in environmental, civil, chemical, mechanical, or electrical engineering — is preferred. Otherwise, a rigorous quantitative training with a degree in the physical, mathematical and/or environmental scicences is required. Prior experiences in one or more of the following areas are of key interest: data analysis; field and/or lab air quality measurements; GIS and spatial statistics, programming and mathematical modeling; and design of electronic and/or mechanical hardware systems.

Our group works hard, is highly collaborative, and has a good sense of fun. We share an overarching motivation to conduct policy-relevant science and engineering that can help address compelling challenges. Through our work, we aim to provide the technical knowledge that enables more effective and informed decisions about the environment and public health. If our group sounds like a good fit for you, please contact Dr. Apte.

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Air quality in India

Particle air pollution in South Asia - especially across the Indo-Gangetic basin in Northern India, Pakistan, Nepal, and Bangladesh - ranks among the most severe in the world. In India alone, hundreds of millions of people are exposed to PM2.5 concentrations an order of magnitude greater than World Health Organization guidelines. However, fundamental aspects of our understanding of particle air pollution in India are incomplete. To inform policies to reduce exposures and improve public health, we are investigating the emissions and physicochemical processes that affect particle concentrations and composition. Our research includes field- and laboratory-based experiments and modeling studies.

Ambient fine particulate matter (PM2.5) levels in Delhi, India rank among the highest levels routinely measured in any city in the world. Annual average PM2.5 concentrations in Delhi are roughly 150 µg m-3, or about 15 times higher than WHO guideline concentrations, and respectively 8× and 1.5× higher than levels in Los Angeles and Beijing. High PM2.5 levels in Delhi are driven by a combination of unfavorable local meteorology and an unusually diverse mixture of local sources. PM sources in the Delhi area are numerous and incompletely understood, but include light- and heavy-duty vehicle traffic emissions and associated road dust, solid fuel combustion for heating and cooking, biomass and waste burning, thermal power plants, diesel generators, construction, and small-scale local industries (e.g., brick manufacturing).

Current projects include: (i) chemical composition and source apportionment of ambient PM in Delhi, and (ii) performance evaluation of lower-cost PM monitoring techniques.

Source apportionment of ambient PM

In collaboration with the Indian Institute of Technology, Delhi, we are investigating the sources and chemical composition of the ambient submicron aerosol (PM1) in South Delhi. Our online measurements consist of particle number size distributions (via scanning mobility particle sizer), black carbon concentrations (via aethalometer) and non-refractory PM1 composition (via Aerodyne aerosol chemical speciation monitor), all collected at 1-5 minute frequency. Using positive matrix factorization (PMF) receptor modeling, we are investigating the local and regional sources that contribute to Delhi's high background concentrations of PM1.

(With Prof. Lea Hildebrandt Ruiz, Chemical and Petroleum Engineering, and Gazala Habib, IIT-Delhi).

Evaluation of low-cost sensors

Lower-cost air pollution sensors have the potential to fill critical air quality monitoring gaps in India and other developing countries. However, few sensors have been rigorously evaluated for their performance in Indian conditions. High PM mass loadings - and the high abundance of fresh combustion emissions from traffic and biomass burning - pose measurement challenges for some lower-cost sensor designs. We have established a fixed monitoring site with reference instruments in order to evaluate and calibrate lower-cost pollution sensors.

(With Prof. Jesse Kroll, MIT).

In-vehicle particle exposures

One important source of air pollution exposure for Delhi residents is time spent in vehicles: many commuters spend 1.5 - 2 hours each day in transit. We conducted an intensive field campaign to measure concentrations of fine, ultrafine, and black carbon particles inside cars and auto-rickshaws in New Delhi. Our measurements showed that particle concentrations in vehicles were 1.5 - 8 times higher than in ambient air. The measured concentrations are among the highest ever reported for a routine transportation microenvironment. 

[Journal article] [Associated Press coverage]

(PhD dissertation project, with William Nazaroff, Julian Marshall, and Thomas Kirchstetter)

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Clean Air and Global Health

Cleaner air, longer lives: Quantifying how air pollution impacts life expectancy

We develop the first systematic estimates of how air pollution shortens life expectancy around the world, taking advantage of a consistent global dataset. The impact of air pollution on human life spans around the world is strikingly large.

[Open Access Journal Article] | [NY Times Article

Citation: Apte JS, Brauer M, Cohen AJ, Ezzati M, Pope CA III. 2018. Ambient PM2.5 reduces global and regional life expectancy. Accepted, Environmental Science and Technology Letters.

Ambient air pollution is a major risk for premature death, killing more than 4 million people worldwide in 2016. While this risk is well understood, few studies to date have systematically evaluated how air pollution shortens lives around the world. We used detailed global data on death-by-age from the Global Burden of Disease 2016 study to quantify how fine particulate matter (PM2.5) air pollution reduces life expectancy at birth (LE) for 185 countries.
We found that the average human loses 1 year of life expectancy because of outdoor PM2.5 air pollution. Exposure to air pollution varies dramatically around the world, and there is generally a larger decline in life expectancy in more polluted countries. In especially polluted countries in Asia and Africa, people die on average 1.5-1.8 years early because of outdoor air pollution. Even in cleaner countries like the USA, current PM2.5 air pollution shortens lifespans by about 0.4 years.
The life expectancy impact of air pollution is large even relative to the impact of many other diseases that are more widely appreciated for their health risks. For example, removing air pollution as a risk for mortality would have a larger impact on lifespans than if major types of cancer — like breast cancer or lung cancer — were completely cured. In some polluted countries, air pollution does more to shorten life expectancy than all types of cancer combined.
The good news is that cleaner air can help bring about longer lives — a finding that has been repeatedly demonstrated through careful analyses around the world. Based on our models, we estimate that meeting the World Health Organization guidelines for PM2.5 air quality globally would lengthen the average human life by about 0.6 years overall, and by more than a year in the most polluted parts of Asia and Africa. Because air pollution has important risks even under the cleanest conditions, even countries that meet the WHO air quality targets could benefit from further improvements in air quality.
Many developing countries face two simultaneous risks from air pollution: on one hand, the outdoor air pollution often associated with industrialization and economic development, and on the other hand, high levels of indoor air pollution from cooking and heating with solid fuels like wood. The combined effect of indoor and outdoor air pollution on life expectancy is very large in places like India, Pakistan, and Bangladesh, where the average life is shortened by more than 2.5 years from the combined result of indoor and outdoor air pollution. In Sub-Saharan Africa, household air pollution has a larger impact on life expectancy than does outdoor air pollution.

Earlier research: Addressing Global Mortality from PM2.5

Journal article: Apte JS, Marshall JD, Cohen AJ, Brauer M. 2015. Adressing global mortality from PM2.5. Environmental Science & Technology, 2015 [open access]

Resources: Press release | High-resolution maps of mortality from PM (PDF, TIFF)

Ambient fine particulate matter (PM2.5) is the seventh-largest global risk factor for premature mortality, resulting in 3.2 million annual deaths in year-2010. To characterize how improvements in ambient PM air quality could result in improved health worldwide, we develop a high-resolution (10-km) model using data and methods from the 2010 Global Burden of Disease (GBD) study. The model combines fine-scale estimates of ambient PM concentrations with regional-cause specific mortality datasets and non-linear integrated exposure-response functions that describe the relationship between PM2.5 and mortality risks.

Improving outdoor air quality — in clean places and in polluted places alike — could potentially avoid millions of worldwide deaths each year. Meeting the WHO 2.5 air quality guideline concentration of 10 µg per cubic meter globaly could avoid up to 2.1 million annual deaths. One striking finding of this work is that comparatively small improvements in PM in already-clean locations (e.g, reductions of 1-4 µg per cubic meter in the U.S. and Europe) could avoid hundreds of thousands of annual deaths, while achieving comparable benefits in polluted developing countries (e.g., China, India) would require much larger improvements in air quality.  However, the potential health benefits of fully meeting WHO guidelines in China and India would be very large, avoiding roughly 1.4 million premature annual deaths from PM.

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