Integrating 24-hour personal monitoring of environmental stressors: a literature review

Personal exposures to environmental stressors are crucial determinants of health but remain difficult to capture due to complex time-activity patterns continuously. In this systematic review, 74 relevant studies were identified from 1836 references in the Web of Science database, where the search combined terms “personal exposure,” “personal monitor*,” “wearable/portable/mobile monitor*/sensor*/device*,” and “24 h*,” “GPS*,” “time activity,” “spatial-temporal” in titles, abstracts, and keywords. These studies, conducted in 39 countries and involving diverse populations (children, college students, working-age adults, pregnant women, and older adults with health impairments), utilized a wide array of personal exposure tools (e.g., nephelometers, aethalometers, MicroPEMs, DustTraks, and low-cost sensors). Continuous measurement intervals ranged from a single day to over six months, enabling researchers to capture diurnal/weekly/monthly exposure patterns across various microenvironments such as homes, workplaces, transit, and leisure spaces. Frequent short-term peaks were consistently linked to activities like cooking, commuting, and biomass-fuel burning in resource-poor settings. Commonly studied pollutants included PM2.5, black carbon (BC), and ultrafine particles (UFP), with PM10, PM1, noise, and multiple gaseous pollutants (CO, O3, NO2, CO2), as well as temperature, relative humidity, total volatile organic compounds (TVOC), and greenspace also featuring in some studies. Compared to central fixed-site stations, personal monitoring often revealed both underestimation (in most cases) and overestimation (in some cases) by ambient/background monitors, depending on infiltration rates, building ventilation, and human activities. Notably, several investigations measuring physiological parameters in parallel found, for example, moderate associations between short-term PM2.5 elevations and acute changes in respiratory or cardiovascular function (e.g., blood pressure, lung function), while personal noise exposure correlated with immediate autonomic responses such as heart rate variability. Overall, these findings highlight that multi-day (≥24-hour) personal monitoring offers a more accurate and fine-grained perspective on exposure patterns than fixed-site methods, particularly among vulnerable subgroups and in environments with complex indoor and outdoor source profiles. By integrating wearable sensors with GPS-based location tracking and/or time-activity diaries, researchers can better identify critical exposure events (e.g., cooking, commuting) and inform targeted interventions—including improved stove technologies, cleaner fuels, or changes in commuting behaviors—to mitigate adverse health outcomes. Continued research is needed to enhance sensor accuracy, validate lower-cost devices, and extend monitoring to a broader range of environmental stressors and larger populations.