Papers of the Month
By Mali Velasco
Tropical cyclones linked to rise in U.S. deaths
Over the last three decades, tropical cyclones in the U.S. were associated with higher death rates in subsequent months, according to an NIEHS-funded study. This is the first study to evaluate cause-specific mortality risks from tropical cyclones in the entire U.S. population.
The study included data on deaths in U.S. counties that experienced at least one tropical cyclone between 1988 and 2018, as well as data from the Social Vulnerability Index, which combines 15 factors that weaken a community’s ability to respond to a disaster, such as poverty and lack of access to transportation. Researchers used a statistical model to calculate how death rates changed after tropical cyclones and hurricanes — a subset of the strongest tropical cyclones — compared with similar periods without these storms.
Residents of 1,206 counties experienced at least one tropical cyclone during the study. In the month following a cyclone, each additional cyclone day was associated with higher county-level death rates for several causes of death, including injuries; infectious and parasitic diseases; respiratory diseases; cardiovascular diseases; and neuropsychiatric conditions. For hurricanes, injury-related deaths increased by 33.4% in the month the storm hit.
Among the study population, the authors observed overall higher death rates in individuals aged 65 years or older, in injury-related deaths for females compared with males, and in the most socially vulnerable counties.
According to the authors, study results contribute to better understanding of how cyclones may affect deaths, providing a foundation for improving resilience to climate-related disasters and climate change.
Citation: Parks RM, Benavides J, Anderson GB, Nethery RC, Navas-Acien A, Dominici F, Ezzati M, Kioumourtzoglou MA. 2022. Association of tropical cyclones with county-level mortality in the US. JAMA 327(10):946–955.
Solar lighting intervention reduces indoor air pollution in Uganda
A solar lighting intervention reduced exposure to fine particulate matter (PM2.5) and black carbon in rural Uganda, according to an NIEHS-funded study. Use of kerosene and other fuel-based lighting contributes to household air pollution in many resource-limited settings. This is the first randomized study to examine whether solar lighting displaces fuel-based options and reduces exposure to harmful substances.
The study included 80 adult women living in rural Uganda. Half of the participants, selected at random, received a home solar lighting system at the beginning of the study. The other half received the system a year later, at the end of the study. The researchers used light and temperature sensors to log use of fuel-based lighting sources and light bulbs powered by solar intervention. They also deployed stationary and personal samplers for 48-hour periods to measure air pollutants.
Among the intervention group, kerosene lamps were completely displaced in 92% of households. The intervention also led to a 37% decrease in PM2.5 and a 91% decrease in black carbon exposures.
The researchers followed up with participants after 12 months, reporting that kerosene lamp displacement and personal exposure reductions were sustained. According to the authors, solar lighting presents an immediate opportunity for reducing personal exposure to indoor air pollutants and should be considered in future interventions.
Citation: Wallach ES, Lam NL, Nuwagira E, Muyanja D, Tayebwa M, Valeri L, Tsai AC, Vallarino J, Allen JG, Lai PS. 2022. Effect of a solar lighting intervention on fuel-based lighting use and exposure to household air pollution in rural Uganda: A randomized controlled trial. Indoor Air 32(2):e12986.
Midlife metal exposure linked to metabolic syndrome in women
Exposure to metals in midlife may contribute to the development of metabolic syndrome (MetS) in women, according to an NIEHS-funded study. Research shows that women in midlife are at greater risk of MetS than younger women. Preventing MetS later in life requires a better understanding of the risk factors involved.
The study included 947 women aged 45-56 years who were free of MetS. The researchers assessed the associations of urinary metal concentrations with MetS incidence annually for 17 years. MetS incidence was defined by subjects having at least three of five components: high blood pressure; fasting glucose levels above the normal range; abdominal obesity; high triglycerides; and low levels of high-density lipoprotein cholesterol, or “good” cholesterol.
Fifteen metals were detected in almost all participants’ urine samples. Higher arsenic, cobalt, and zinc concentrations were significantly associated with elevated MetS incidence over the study period. These associations persisted after controlling for demographic, socioeconomic, and lifestyle factors; menopausal status; and body mass index. Exposure to mixtures of several metals was also associated with higher MetS incidence.
According to the authors, metals may contribute to MetS development. They note that more studies are needed to confirm these findings and to investigate the underlying biological mechanisms.
Citation: Wang X, Karvonen-Gutierrez CA, Herman WH, Mukherjee B, Park SK. 2022. Metals and risk of incident metabolic syndrome in a prospective cohort of midlife women in the United States. Environ Res 210:112976.
Link between placenta and fetal brain may predict neurodevelopment disorders
A new NIEHS-funded study in mice showed that prenatal exposure to polychlorinated biphenyls (PCBs) altered DNA methylation in both the placenta and fetal brain in a manner consistent with neurodevelopmental disorders. DNA methylation is a molecular mechanism that regulates the function and expression of genes.
The placenta is responsible for removing toxicants to protect the developing fetus, but PCBs can cross the placental barrier. The team aimed to determine whether changes in the placenta may serve as a predictor of DNA methylation in the brain.
Researchers exposed mice to PCBs through diet before conception and during pregnancy and assessed the effects on DNA methylation. They observed altered DNA methylation in thousands of regions — called differentially methylated regions (DMRs) — in the placenta and fetal brain of PCB-exposed mice compared with controls.
PCB-associated DMRs in the placenta and brain overlapped significantly and housed a shared subset of genes that control pathways important in cell differentiation and neuron growth. Researchers observed that these regions had an overrepresentation of genes previously associated with neurodevelopmental and autism spectrum disorders in humans.
According to the authors, DNA methylation profiles of placenta with measured PCB exposures could serve as predictive biomarkers to enable early intervention of PCB-associated neurodevelopmental disorders.
Citation: Laufer BI, Neier K, Valenzuela AE, Yasui DH, Schmidt RJ, Lein PJ, LaSalle JM. 2022. Placenta and fetal brain share a neurodevelopmental disorder DNA methylation profile in a mouse model of prenatal PCB exposure. Cell Rep 38(9):110442.
(Mali Velasco is a research and communication specialist for MDB Inc., a contractor for the NIEHS Division of Extramural Research and Training.)