Researchers from the Carlos III Health Institute (ISCIII) have focused, in a new work, on the role of ozone generated by wildfires in the increase of urgent hospital admissions for all kinds of causes and, in particular, for respiratory and circulatory problems linked to these episodes.
The study, published last year in the journal "Science of The Total Environment," has been presented by two of its signatories and co-directors of the Reference Unit on Climate Change, Health, and Urban Environment of ISCIII, Cristina Linares and Julio Díaz, during an informational session convened by SMC Spain.
The research group evaluated the short-term effect of nitrogen dioxide (NO2), ozone (O3), PM10 and PM2.5 particles, and temperature during a heatwave on urgent hospital admissions in Spain, focusing on days with active wildfires.
The results show that ozone is configured as an "invisible enemy" for health during wildfires: in the period 2013-2018, and in the nine analyzed provinces (A Coruña, Balearic Islands, Las Palmas, Madrid, Málaga, Sevilla, Valencia, Vizcaya, and Zaragoza), it was associated with more than double the hospital admissions than PM smoke particles, on which most warnings tend to concentrate.
"The recommendations are always not to expose oneself to smoke, to protect oneself with a mask, of course, to stay indoors, not to exercise or engage in activities that require respiratory effort, but it is never talked about how those ozone peaks, which can also occur in places very far from the fire's focus due to atmospheric chemistry, can contribute to the increase of those urgent hospital admissions, that is, within one, two, or three days after the fire is declared," explained Cristina Linares.
In global figures, 8,018 hospital admissions were attributed to O3, 5,982 to NO2, and 3,813 to PM particles. In the case of respiratory pathologies, admissions linked to PM10 rise from 0.8 percent on days without wildfires to 13.9 percent when there are active fires, while admissions related to O3 increase from 8.3 percent to 21 percent. For circulatory causes, the work found no statistically significant differences attributable exclusively to smoke.
Linares and Díaz have emphasized that the analysis does not allow for demonstrating causality and that the hospitalization records used did not include data on the patients' prior health status. In this regard, they recall that the smoke from fires does not affect a healthy person in the same way as someone with risk factors, so it is considered that the majority of emergency room visits correspond to patients with pre-existing cardiorespiratory disease or to vulnerable populations, such as children, pregnant women, and elderly people with comorbidities.
Implications for public health and planning
Based on these conclusions, Linares has insisted that early warning systems to the population in the event of a fire must also incorporate exposure to pollutants such as ozone, in addition to particles. "That is to say, not only directing measures to the protection of particulate matter but also to evaluate and monitor ozone levels, since we know it is the pollutant that most influences those hospital admissions during fires," he has indicated.
For his part, Julio Díaz has pointed out that the work provides evidence of the spike in admissions after fires, so it should serve to improve prevention and health planning, allowing for the adjustment of hospital resources in advance to the anticipated increase in demand. The researcher has recalled that this "is already being done" and has cited the collaboration with the Hospital Universitario La Paz to create a model for predicting urgent admissions due to respiratory, circulatory, or neurological causes based on environmental indicators.
"We already know that there is an increase in admissions when these combustion episodes occur and which pollutants are most attributable. Now what needs to be set up is, from my point of view, a monitoring and surveillance plan, especially to reinforce hospital services, in which specialties need to be strengthened," Linares has added, emphasizing that this anticipation would help avoid the collapse of emergency services.
In addition, Linares has encouraged regularly consulting the air quality monitoring networks and demanding real-time data from the administrations, as well as integrating the plans against heat waves and the air pollution plans into a single strategy. "Because we know that these are the two risk factors that are acting determinately on people's health," he has specified.