The vast majority of earthquakes strike inside the , a string of volcanoes and tectonic activity that wraps around the coastlines of the Pacific Ocean. But when an earthquake hits, the areas that experience the strongest shaking aren鈥檛 always the places that suffer the greatest damage.

Take the massive , which caused extensive damage in Taiwan in the fall of 1999 and killed more than 2,400 people. The distribution of damage followed an uneven pattern: Deaths caused by the earthquake were concentrated not in densely populated city centers, but in those cities鈥� suburbs and outer fringes. A similar pattern has occurred following earthquakes in China, Chile and Nepal.

More than two decades later, researchers at the 糖心少女 have identified a hidden factor behind what they call 鈥榮uburban syndrome鈥� 鈥� migration. Workers from small, rural communities often move into the outer edges of cities, which offer greater economic opportunities but often have low-quality housing that is likely to suffer greater damage during an earthquake. The risk grows even more when migrants come from low-income or tribal villages.

The findings, , suggest that emergency management organizations should pay greater attention to migration and housing quality when developing disaster mitigation and response plans.

糖心少女News spoke with lead author , an assistant professor of environmental & occupational health sciences and of urban planning, to discuss 鈥榮uburban syndrome,鈥� how migration can amplify disparities in a disaster鈥檚 impact, and what U.S. officials can learn from a Taiwanese disaster.

Your work on this study builds on an existing model that assesses earthquake risk by considering migration patterns and the movement of vulnerable populations. What does the existing model miss, and why is it important to fill those gaps?听听

Tzu-Hsin Karen Chen: This risk-assessment model has been used by many organizations internationally and in the United States. For example, FEMA uses a similar risk model to assess populations exposed to hazards, vulnerabilities and potential disaster impacts. They typically do a comprehensive risk assessment geographically within states and counties, identify areas with potential larger impacts, and then draft a preparedness plan.

In United States, temporary domestic migrants and undocumented immigrants don鈥檛 always officially register in government systems. One common reason is the fear of deportation or other legal repercussions. And so, when a government agency like FEMA allocates resources for disaster preparedness or recovery, relying on registered population data can lead to an underestimate of the support required in certain areas.

In Taiwan, our study case, many migrant workers moving from rural to urban areas don鈥檛 update their registered residence. They still have their registration back in their hometown, like in a tribal area. It just doesn’t make sense to re-register, because they might have multiple jobs within a single year in different places. To minimize expenses, some workers look for the lowest possible rent, and their rental housing might not be officially registered either. Those could be informal housing structures, like a metal floor added on top of a concrete building, which don鈥檛 comply with safety regulations. The informality of this process can help lower their cost of living, but can also leave them more vulnerable to disasters.

How did you get started in this research?听

TKC: I鈥檒l share my personal story, but I also want to acknowledge my co-authors for their years of work in risk assessments. For me, it started back in 2010, when I volunteered in a tribal area of Taiwan teaching computer skills. This provided bigger lessons for me than anything I could鈥檝e taught them. I learned how teenagers often move from their tribal areas downhill to nearby cities to take construction jobs during the off-crop seasons. Those jobs pay more than farm work, but they鈥檙e also very physically demanding and often lack worker protections like job security and health insurance. Seeing that put a seed in my mind.听

When I was a master鈥檚 student, a team from the National Earthquake Center and Academia Sinica in Taiwan was working on a risk assessment of the Chi-Chi earthquake using the exposure, vulnerability and hazard framework. They had already published a fundamental , and reached out to me to develop an extended study by incorporating spatial statistics. That collaboration eventually evolved into the study in this paper.听

The COVID-19 pandemic also shaped this study. I came across news about how migrant workers were stuck in urban fringe areas of India. Because of the lockdown, they weren鈥檛 able to continue their work, and their crowded living conditions left them at even greater risk during the pandemic. I started to wonder: How can we shift from a pure statistical model to something more meaningful? How can we bring migration into the center of the discussion?听

The final push came from colleagues鈥� work at the UW. I鈥檝e noticed initiatives for undocumented students and research efforts around environmental justice and health equity. For example, my co-author 鈥檚 research on migrant worker鈥檚 health was particularly motivating. We read and wrote back and forth to refine the framing and discussion in this paper. 听

How did you incorporate migration data into a larger earthquake-risk model, and what did you find?

TKC: At the time of the Chi-Chi earthquake in the late 1990s, we didn鈥檛 have any detailed migration data. Today, new research uses mobile phone signals to track people, but such data wasn鈥檛 available back then. So we adapted the 鈥� a model widely used to predict human migration 鈥� to estimate migration flow and used it as a new way to estimate migrants from low-income and tribal areas. This provided new variables to incorporate into the large risk model.听

Most of our findings are supportive of previous studies, where we can see, logically, if there鈥檚 stronger ground movement, there are likely to be more fatalities. That鈥檚 a very straightforward way of thinking of how disasters can happen. However, it鈥檚 not just a physical story. We also confirm that in areas where incomes are lower, there are more fatalities. Income is a known risk factor in the vulnerability theory. What鈥檚 unique in this study is that we tested whether an increase in migration flows leads to an increase in fatalities, and we found that to be true.听

Tell me about the migration model. What is it estimating?听

TKC: We applied the radiation model and adapted it to measure different migration populations. The fundamental idea of the radiation model comes from a simple model called the . In this context, gravity refers to the idea that larger populations have a stronger 鈥減ull鈥� on people in nearby communities. The model assumes that, for a place, the number of people who want to migrate to nearby cities depends on the population size of those cities. Larger cities tend to attract more people.听听

If the distance is too far, then it costs too much to travel, so the model will predict fewer migrants. But if the city is closer, or even far away but has a very large population, it becomes a more attractive destination, leading to greater migration flow.听听

The radiation model builds on these principles and adds another layer. It considers competitors along the way. In other words, migration flow may also be influenced by other cities or opportunities that lie between the starting point and the destination.听

At first glance, it seems obvious that greater migration would lead to higher fatalities in a given area, just because there are more people present when disaster strikes. Is that the primary driver, or are there other factors at play?听听

TKC: Logically, if there are more people, and the percentage of fatalities is equal, then there should be more people dying from a specific event. But we found it鈥檚 not just about population numbers. There are two additional factors: When migrant workers are from areas with lower incomes, or when they are from tribal areas, those factors significantly contribute to higher fatalities in the places they migrate to.听

Our hypothesis is that it鈥檚 about housing safety. Migrant workers tend to move to cities, and when cities are more expensive, affluent workers might be able to secure housing that offers better protection against disasters. However, workers from tribal or low-income areas tend to settle in urban fringe zones where affordable housing options might not meet safety standards, making them more vulnerable to earthquakes.

Why did you choose to study this earthquake from 1999 in particular?听听

TKC: The research team that invited me to work on this project was interested in the Chi-Chi earthquake, partly because it was one of the most disastrous in Taiwan鈥檚 history. And even 20 years later, there鈥檚 still a conference focused on the Chi-Chi earthquake that brings domestic and international researchers to talk about it.

How widely applicable are your findings? Could they help us better understand hazards in other earthquake-prone areas of the world, like, say, the Pacific Northwest?听听

TKC: It鈥檚 important to consider this risk assessment as a tool for preparedness for future hazards. When the next earthquake occurs, migrant communities will likely face elevated impacts if housing safety policies do not improve.

I believe the migration component is universally important, even outside Taiwan. There has always been a paradox, a structural dilemma of disaster governance: Because migrants are often invisible, they suffer from little support. But making them visible can sometimes lead to exclusion and discrimination. This model represents migrants in a geographic sense rather than identifying every person individually through government surveillance, which could address this challenge. By protecting anonymity while still accounting for migrant populations, the model might help ensure their needs are considered in housing safety and resource allocation.

Co-authors on this study include Diana Ceballos of the 糖心少女Department of Environmental & Occupational Health Sciences; Kuan-Hui Elaine Lin of National Taiwan Normal University, Thung-Hong Lin of Academia Sinica in Taiwan; and Gee-Yu Liu and Chin-Hsun Yeh of the National Center for Research on Earthquake Engineering in Taiwan.

For more information, contact Chen at kthchen@uw.edu.

You know that nail salon smell? That sharp hit of chemicals, the strangely sweet scent of polish, the faint tingle in your nose? That鈥檚 air pollution, and it鈥檚 been linked to a variety of experienced by the workers who breathe it. Nail salon workers commonly experience irritated skin and eyes, headaches, loss of smell and respiratory problems.听听

Officials in some cities and states, including Washington, have introduced new regulations designed to better protect nail salon workers 鈥� .听

But the mysteries around what, exactly, causes those potent smells make protecting these workers more difficult. Cosmetics manufacturers are rarely required to disclose what specific chemicals they use to scent their products, which has hindered efforts to better understand the air that salon workers breathe. 听

, a 糖心少女assistant professor of environmental and occupational health sciences, set out to solve the mystery. In a study published , Ceballos and her co-authors analyzed the air in a group of nail salons around Boston 鈥� where Ceballos previously worked at Harvard University 鈥� and identified 18 distinct fragrance chemicals. It鈥檚 the most comprehensive study to date of the specific fragrance chemical mixtures found in nail salon air, and will allow researchers to further study the potential health risks.

糖心少女News sat down with Ceballos to discuss the findings of the study, the mysteries around fragrance chemicals and how to better protect nail salon workers鈥� health.听听

Nail salons are a bit of a research specialty of yours. You鈥檝e published papers on , workers鈥� exposure to 鈥渙ld鈥� and as well as 鈥�鈥� harmful chemicals, and the . How did you come to focus on nail salons and their workers? 听

Diana Ceballos: I started working on nail salons soon after I read a back in 2015. It won all sorts of awards. When that story came out, it created havoc. I was working at the Centers for Disease Control and Prevention at the time, and the New York Health Department asked for technical assistance because they were horrified by the conditions in nail salons. I was put on the team partly because I鈥檓 an industrial hygienist, but also because I speak Spanish, and there are a lot of Spanish-speaking workers in these salons.听听

Then my life changed, and I went back to academia. I just knew there was more we could be doing. There was just so little research in this area, it was incredible. So, I decided I wanted to focus on nail salons. In the meantime, a lot of other people had the same idea, so lots of different groups around the country and internationally have started working on this.听听

What are fragrance chemicals, and what do we know about them? 听

DC: Fragrances are added to nail salon products to create a desired smell 鈥� lotion that you want to smell like lavender, for example 鈥� but many fragrances are used to mask undesired smells. A lot of nail products have very strong, not-so-good smells, so companies add fragrances to mask those smells. But then you have even more scented chemicals in the air!听

A good number of fragrances are known sensitizers. That doesn鈥檛 only cause irritation on the skin, but, for example, some fragrances could trigger an asthma attack if inhaled. Or, if they鈥檙e a sensitizer, they could even help cause asthma and other respiratory complications. It鈥檚 not just the skin, it鈥檚 the entire immune system. And that鈥檚 just the effects that we know of.听

There are also some positive effects from fragrances. It鈥檚 well-known that some fragrances can be relaxing or affect the ambiance of an environment. But that hasn鈥檛 been well-studied. Some of these chemicals are very little-known. They could be toxic, but we don鈥檛 know. They鈥檙e just used in small amounts to produce fragrance, and for the most part, chemical regulations have been focused on bigger culprits. It鈥檚 just in the last decade or so that officials have paid attention to chemicals that show up in smaller quantities, like fragrances.听

For a very long time, fragrances were trade secrets, and specific chemicals weren鈥檛 listed as ingredients. Labels just said 鈥榝ragrance.鈥� In the last 10 years, chemical regulations in Europe and in some states have introduced more discrimination of toxic chemicals that could include fragrances, but there鈥檚 a lot of work still to disclose the ingredients. For example, in the new cosmetics bill in Washington, there鈥檚 more information required on ingredients lists. That was already the case in California, for example, but it鈥檚 just starting. We aren鈥檛 the first ones to ever measure them, but to our knowledge we鈥檝e measured the biggest number of fragrances. Also, our analysis suggests that not only nail products are contributing to fragrances, but also other products in the salons such as personal care products and cleaning agents are potential emission sources.听

Many people can identify the strong scent of a nail salon, but I鈥檓 not sure we consider that we鈥檙e actually smelling air pollution. How does that pollution affect nail salon workers?听听

DC: Indoor air quality is important for anyone. The quality of our health depends on the air that we breathe. Even for a customer, nail salons are very fragrant and have many odors. Some people are very sensitive to odors. Even just talking about the odor itself can trigger a lot of health effects. People can get headaches, dizziness, and get nauseated. So, there are people that don鈥檛 go to nail salons because they can鈥檛 be in there. And that鈥檚 a customer. Imagine the workers. 听

There are people who have to do this work because they don鈥檛 have training in anything else, and in surveys of the health of people who work in nail salons, it鈥檚 fairly prevalent to have headaches, irritation, fussiness 鈥� all the typical symptoms of odors, let alone toxic chemicals. It can deteriorate your well-being and quality of life, especially as some of these workers are on 12-hour shifts, seven days a week. So, it鈥檚 significant, the amount of time they鈥檙e exposed to these fragrances along with many other toxic chemicals.听

You note throughout your research that the air pollution in nail salons is something that can affect the air we all breathe 鈥� even if we never visit a salon. How is that possible?听

DC: It鈥檚 very important to lower chemical concentrations indoors because they eventually go outside and contribute to overall air pollution. It鈥檚 hard to control that in small businesses, but one thing that was clear when Boston was building a ventilation policy was that it was important to make sure businesses filtered out chemicals before they went out the window. Now we know that fragrances make up a considerable part of overall chemicals in nail salons and they鈥檙e adding to the mix. And since you have fragrances in a bunch of products, it all adds up. We must consider the accumulated burden that fragrances can have in the indoor environment and put more purposeful thought into how we produce products that contain those things 鈥� not just during the life cycle of the products, but also how they interact with the environment. 听

There are policies right now that are trying to work on fragrances, but we need to learn more. It鈥檚 going to be a while before we can control or guide manufacturers better. It鈥檚 very early, but I think there鈥檚 a lot we can learn about fragrances in the future.听

Other authors on the June 19 paper are Chunrong Jia and Xianqiang Fu of the University of Memphis and Thomas Webster of Boston University.听听

For more information or to reach Ceballos, contact Alden Woods at acwoods@uw.edu.听