Heat waves in Mexicali, Baja California, Mexico: morbidity, mortality and vulnerability to heat

Abstract

(DL).Disasters are occurring more frequently throughout the world and the loss of human lives due to them is increasing considerably. Strictly speaking, disasters are not natural, but are due to the presence of a natural phenomenon combined with the presence of man in his environment. In the case of atmospheric or climatic phenomena, they can generate a disaster when society and ecosystems are incapable of dealing with them efficiently; such is the case of heat waves, which, on multiple occasions, in many countries have become public health disasters. Heat waves are periods of unusually hot and dry or hot and humid weather, with a subtle onset and cessation, lasting at least two or three days, responsible for a high mortality and morbidity rate and varying in character and impact even in the same locality, i.e., they are relative to the climate of a place. The capacity for climatic adaptation added to demographic and socioeconomic characteristics can determine an individual level of risk; heat waves are more likely to impact the following vulnerable populations: the elderly and children, individuals with pre-existing disease conditions, living in social isolation, without air conditioning, homeless, not having access to timely information on temperatures and health effects, being unable to move, suffering from a mental illness, not being able to take care of oneself, and poverty in urban areas. Likewise, heat waves will increase in intensity, duration and frequency according to global and regional climate scenarios. Therefore, in this article, in the period from 2002 to 2023, we proposed to quantify the role that heat waves have had on the health of the inhabitants and to evaluate human vulnerability to heat by estimating a physical risk index. Mexicali, Baja California, Mexico, was chosen because it is the city with the highest temperatures in the country during the summer, and health problems occur annually as a result of these extreme hot temperatures. For this purpose, two approaches were used. The first one was oriented to quantify the health effects caused by extreme hot temperatures, through the weekly epidemiological bulletins that the Ministry of Health, which is part of the Mexican government, has available for any user interested in obtaining it; the information on health effects was complemented with local studies, which are supported by local health institutions and the forensic medical service. The second approach was oriented to estimate the physical risk due to extreme heat temperatures using physical and social vulnerability criteria by basic geostatistical areas. It was found that due to the heat waves the total number of people affected was 1054, of which 418 (39.7%) were from heat stroke, 627 (59.5%) from heat exhaustion and 9 (0.8%) from sunburn. Due to the grouping of heat stroke by the Ministry of Health, which includes heat stroke, not all deaths are reported in this classification. Deaths, certified by the medical examiner, totaled 332, with a maximum value of 45 in the year 2023. The physical risk index confirmed that the areas most vulnerable to heat are located in areas of the city of Mexicali where the socioeconomic level is low, with deficiencies in basic public services and the population has a low income. It is concluded that heat waves in Mexicali are a public health problem and that a possible solution for their mitigation is a strategic planning in which government, academia and companies participate, linked to a communication network, both through governmental dissemination and the use of social networks. It is also proposed the creation of more green areas and/or urban reforestation in the most vulnerable areas, which could serve as a resource to reduce the intensity of the urban heat island and the intensity of the heat waves, and thus generate comfortable areas within the city.