Extreme Heat and Air Pollution (HEAL) Lab

Extreme heat and air pollution kill!

Category: Research

Publication Alert: How does irrigation impact heat stress on farmworkers?

By

On December 26, 2024

In Regional Climate Modeling (WRF-Chem), Science/Academic

How does irrigation impact heat stress on farmworkers?

We answer the above question in quite detail in our freshly pressed article in Nature Communication Earth & Environment. It is an open-access article and thus freely accessible to everyone:

https://www.nature.com/articles/s43247-024-01959-7

We used a regional climate model (WRF) set up at 1-km resolution to calculate Wet Bulb Globe Temperature (WBGT), a standard metrics of heat stress, using ECMWF’s thermofeel python library, and examined the impact of irrigation on heat stress in Southern California’s key agricultural region, the Imperial Valley. Our main conclusions are:

1. Irrigation reduces heat stress in the daytime but increases it at night.

2. Urban and fallow areas adjacent to the cropped fields also experience increased heat stress due to moisture advection from irrigated areas.

Some background about this work

According to a recent OEHHA report, heat related illnesses among farmworkers are the highest in the Imperial County in the entire California.

Imperial Valley is not a small area, the entire county is a cultivated field. That is roughtly the size of 7, 37, 000 football fields. No wonder, Imperial Valley produces about two-third of the winter vegetables and up to one-third of the fruits and nuts consumed in the US.

There are nearly a million farmworkers employed in the Central and Imperial Valley region. They are exposed to high heat stress everyday as they get involved in various agricultural activities from planting to harvesting to packaging, between late Spring to early Fall season.

One of the unique thing about the Imperial Valley is that irrigation is heavily applied in its cropfields – thanks to the All American Canal built in the 1930s. The amount of irrigation applied here (~ 5 ft) is more than 20 times greater than its annual rainfall (~3 inches).

Given such a large amount of irrigation applied in its cropfields, a natural question came in our mind. Does the irrigation affect heat stress experienced by farmworkers? If yes, when, where, and how? We try to answer these questions in the above article.

Please stay tuned for what is next. We are working on a follow-up article in which we calculate rest-break requirements for farmworkers using the same high-resolution climate model outputs. We are trying to help redefine California’s heat related policies to protect the outdoor workers.

Hats off to our food producers, the toughest and the most resilient, the farmworkers!

Thank you for reading this! Merry Christmas and happy holidays to you all!

Funding for this work was generously provided by University of California Office of the President under the project Rural Heat Island:
https://lnkd.in/g5WVqWrf

Parajuli, S.P., Biggs, T., de Sales, F. et al. Impact of irrigation on farmworker’s heat stress in California differs by season and during the day and night. Commun Earth Environ 5, 787 (2024). https://doi.org/10.1038/s43247-024-01959-7

Imperial Valley Environmental Justice Summit

By

On October 24, 2024

In Dust, Climate, Environment, and Society

Some 100 miles east of San Diego, lives a big agri-town called Imperial Valley (IV) that supplies 2/3 of the winter vegetables and 1/3 of the fruits/vegetables consumed in the entire US. Majority of IV residents are hispanic with 25% living below poverty line and the majority of farmworkers are migrant workers coming from Mexicali across the US-Mexico border. IV has high rates of asthma (one in five children) and the highest heat-related illness rate in the entire state. Several environmental threats contribute to these issues, including the harsh desert climate, the shrinking Salton Sea, blowing dust storms, pesticides-laden runoff from highly irrigated lands, agricultural activities that produce dust and smoke, rapid urbanization, industrial expansion, and now the lithium exploration activities.

State and Federal government representatives, local NGOs and community members, researchers, and most importantly, the farmworkers, met to discuss about how to deal with the emerging environmental challenges of the region in an event called EJSummit. The Environmental Health Leadership Summit (EJSummit) is an annual event organized by a local community organization called Comite Civico del Valle now in its 13th year. The event occured on October 22/23 this year, right next to the agricultural fields of the IV in El Centro, CA.

Following points were noted:

  1. The hot brine below the Salton Sea (not the Salton Sea water) has enough Lithium to meet 1/3 of today’s global demand. The proposed Direct Lithium Extraction method extracts lithium from brine directly using more environmental friendly technique using a adsorption material thereby rejecting the brine which is reinjected underground, but the technology has not been implemented in industrial scale so the reality of anticipated ‘Lithium Valley’ is yet to be realized.
  2. The Salton Sea continues to shrink due to high rate of evaporation combined with reduced inflow of water caused by the Quantification Settlement Agreement (QSA) of 2003 that diverted some 15% water to San Diego region. The local people mentioned that many people have lost their jobs due to reduced agricultural activities, caused by the reduced water inflow to the IV crop fields.
  3. Speakers included 84-year old living legend Preston Arrow-Weed (in picture), a member of Kumeyaay tribe, who lived in this region for thousands of years. Who else can better teach how to reduce our environmental footprint and to live in harmony with nature?

Summer is approaching its peak, are you prepared?

By

On June 25, 2024

In Dust, Climate, Environment, and Society

I almost dozed off on a red light yesterday. What could be the reason?

Myself during the installation of heat stress sensors (black globe thermometer, temperature/humidity sensors, and pyranometer) in Imperial Valley, CA in May, 2024.

I don’t turn on my A/C to save cost, energy, or environment whatever one might think of, unless it is unbearably hot. I only turn on the fan. Yesterday was not an extreme day anyway. Just a normal weather day in the upper 70s. And my car is always parked indoor whether at home or office. And I had enough rest for sure. So what else could be the reason?

May be CO? We know that exposure to carbon monoxide can make us sick and even unconscious depending upon the concentration. Where else can be its greatest risk, other than in a car?

May be Oxygen? We know that low oxygen level can also make us sick. Again, where else can it be lower than in an enclosed box? Oh sorry, I forgot about the high mountains.

May be heat? We all know this is also a possibility. We see more people dozing off in summer everywhere, even in meetings and conferences. :).

May be many of you have also experienced something similar. If it happens during a 15-minute drive, imagine what those long haul drivers have to go through, who have no choice but to drive for more than 12 hours everyday. I am 100% sure, coffee can’t solve this problem, however big your cup may be. This is especially critical in summer.

It could be any or all of the above factors. But summer heat is probably the most likely factor here.

With the above context, the question I would like to ask today is why the heat-related deaths are much higher in the developed countries than in developing regions such as Africa or India? As far as I know, the most intense heatwave in the recent history in India occured in 2015 and only about 2500 people died when the maximum temperature rose close to 50 degree celsius. In contrast, more than 60,000 people died during the heatwaves of 2022 in Europe when the maximum temperature rose to something similar.

Humidity has a role to play on heat stress, and the data from India may not be accurate for various reasons, but these factors can’t explain such an order of magnitude discrepancy.

What could be the main reason?

The answer has to lie in our modern way of life. We are spending most of our times indoor which is interfering with our body’s ability to acclimatize. We, the city dwellers, have become a new species that can only survive within a very narrow range of temperature T±ΔT.

The term acclimatization probably needs to be redefined. Traditionally, it referred to how people adapt to different climate regions based on geography. But now, because of our HVAC way of life, the exposure to high temperature is more based on indoor vs. outdoor temperatures than the temperature in region1 vs. region2.

The way we define heatwaves also needs to be reassessed. Normally, it is defined based on how far is the daily maximum temperature from the historical average value in a given location. But, with our indoor way of life, the average base temperature needs to represent our ‘indoor’ temperature where we spend or live most of our time. Obviously, it is going to be different for different people. It might even be associated with social structure and poverty level—just my naive guess.

It is not only about heat, it is also about oxygen level. Although oxygen is the most vital element of life, it’s study has received the least attention for some unknown reasons. One such eccentric study (I wonder how they received the funding) in a Journal of American Chemical Society, the oxygen level is declining in large cities globally, and that the increase in heatwave occurrence was correlated with reduced oxygen level.

Increasing number of studies are showing that air pollution, oxygen level, extreme weather events, occurrence of heatwaves, energy demand all of these are correlated. Our environmental problems have become much more complex nowadays. We need to rise above our traditional area of expertise and think differently if we want to solve these problems. We have to put all these pieces of the puzzle together to know whether the puzzle is a tiger or an elephant.

Together we can.

Heat stress sensors installation in the Imperial Valley

By

On May 9, 2024

In Research, Sustainable living/Health

We have deployed two sets of instruments to our field sites at Westmorland, Imperial Valley in coordination with the University of California Cooperative Extension (UCCE) office at Holtville, CA. Each station has a black-globe sensor, relative humidity and temperature sensor, and pyranometer. Together, these measurement will be used to calculate Wet Bulb Globe Temperature (WBGT), a key indicator of heat stress on humans.

Installation of heat stress sensors at Westmorland, Imperial Valley.

We have also installed one station at an urban site in El Centro, Imperial Valley in cooperation with the Air Pollution Control District (APCD), El Centro office. The station is located on the roof of the APCD building.

Station at APCD, El Centro building.

Working for ~4 hour in the sun for the instrument installation in this early May was not easy. Imagine farmworkers working in the field everyday regardless of heat, wind, or dust.

Foods do not come to our table so easily. They do not grow in the grocery stores either. A lot of sweat, hardwork, and endurance involved. We must treat farmworkers and the soil with respect if we want quality food on our table.

PS: We are grateful to our collegues at UCCE, Hotville and APCD, El Centro for facilitating installation of our instruments in their sites.

Cloud seeding and weather modification

By

On January 25, 2023

In Dust, Climate, Environment, and Society

Imagine a world without rainfall. We call it droughts. Or imagine a situation of torrential rainfall and flooding, like in Pakistan last year.

And imagine a world where all our groundwater reserves have dried up. This is not too hypothetical a scenario — the world’s groundwater reserves are already declining. Groundwater is no different from fossil fuels – it is going to deplete one day if we continue to extract without allowing it to recharge.

A drought does not kill in hundreds – when it happens, it kills millions. China, India, Bangladesh, Africa, and even Russia and USA have faced such droughts in their history. And flooding has similar consequences – it causes extensive loss of lives and properties.

So what can we do to prepare ourselves for such adverse scenarios or natural calamities? How can we make sure that we have enough freshwater resources to meet the demand of an ever-increasing population which is already 7 billion?

Cloud seeding is one potential solution. Cloud seeding can be used both to suppress or enhance rainfall. If used appropriately, the application of cloud seeding technology has many possibilities — from enhancing rainfall, snow packs, and groundwater reserves — to suppressing hails, the great enemy of farmers, which can destroy large crop fields in minutes. Cloud seeding is relatively a mature technology used since the 1950s when scientists first discovered the seeding ability of dry ice and silver iodide. It was extensively applied in the late 20th century but it slowly lost momentum afterward for various reasons. Its exploration is again gaining attention as we face prolonged droughts, heatwaves, flooding, and fires worldwide.


This week, scientists and policymakers from around the world working in the field of cloud seeding and rain enhancement are meeting in Abu Dhabi to discuss these and other related issues aiming to find water solutions for the future.



On the first day of #IREF organized by The UAE Research Program for Rain Enhancement Science (UAEREP), we saw several interesting new approaches in cloud seeding works, from the use of electrical charge to acoustic methods for rain enhancement. Today was another engaging day discussing the process-level understanding of aerosol-cloud interactions and the adoption of cloud seeding technology by countries such as Ethiopia and Thailand for tackling their water problems. For anyone interested in understanding rain enhancement technologies, below is the link to today’s program.

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