Evidence Regarding Weather Modification

A rapid search in major biomedical research databases reveals limited knowledge on the matter. The majority of studies document environmental impacts of cloud seeding but provide limited information regarding its actual effect on human health. In this sense, it has become obvious that WM can lead to increased air stagnation over residential areas, particularly during winter, ^{Reference Liao, Gui and Jiang3,Reference Garrido-Perez, Ordóñez, García-Herrera and Barriopedro4} as well as to a decrease in the photosynthetic ability of terrestrial plants and phytoplankton. ^{Reference Rodríguez-Sánchez, Rosas, Calva-Vásquez and Sandoval-Zapotitla5,Reference Fajardo, Costa and Ortiz6} The available studies have also examined the distribution of particles used for the purpose of WM in atmospheric air ^{Reference Lou, Zhao and Yang7} or in the water ^{Reference Deng, Shi and Wu8} and novel cloud seeding techniques capable of decreasing the amount of greenhouse gases trapped by the clouds. ^{Reference Storelvmo, Boos and Herger9} Such studies provide a standpoint for hypotheses and predictions and show a considerable knowledge gap with regard to WM safety and potential health benefits.

To date, not only studies on toxicity of compounds used in cloud seeding are limited, but also some of them have gained expressions of concern or been retracted on the grounds of scientific integrity. ^{10,Reference Herndon11} It appears that WM-associated air stagnation can trigger asthma exaggeration, ^{Reference Norris, Larson and Koenig12} while manual treatment of cloud seeding compounds increases the risk for occupational contact dermatitis. ^{Reference Ng and Koh13} Until a large-scale investigation of the real-world health implications of WM means and techniques is performed, relevant public health preparedness needs to be based on the existing knowledge about the interconnection of climate, climate change, and climate adaptation on human health.

Health Considerations on Weather Modification

Climate conditions can have direct and indirect effects on health. Direct health implications include respiratory disease exacerbation, skin and eye inflammation due to low air humidity, ^{Reference Sato, Fukayo and Yano14} blood pressure and heart rhythm irregularities due to low or high temperatures, ^{Reference Liu, Yavar and Sun15} and altered transmission dynamics in cases of weather conditions favoring indoor gatherings or proliferation of zoonotic disease vectors and radiation-associated skin cancer. ^{Reference Joszt16} Indirect health implications stem from climate change intercepting the social determinants of health. Increased temperatures, reduced rainfall, droughts, and the opposites of them can equivocally harm agricultural economy, travel and tourism, undermine food security, professional and financial stability, and pave the way toward irregular migration. ^{Reference Semenza and Ebi17} Simultaneously, the provision of health care services is also subject to adverse weather conditions that hinder the commute of health care professionals, patients, and supplies, or destroy sensitive equipment. ^{Reference Paavola18}

While WM is regarded as reparative action toward the aforementioned climate conditions, it is still likely that efforts to decrease the temperature or induce rainfall can backfire in the form of freeze damage and floods, and vice versa. For instance, cloud seeding over remote agricultural communities with a high prevalence of respiratory and cardiovascular diseases and limited access to emergency health care may undermine the benefits from increased crop production. Similarly, unexpected rainfall or snowfall can pose a threat to remote communities, who will be deprived of supplies or access to emergency care. ^{Reference Friedrich, Ikeda and Tessendorf19} Providing remote communities with adequate supplies, instructing people with respiratory conditions to wear a mask or stay indoors, enhancing epidemiological surveillance for zoonotic disease outbreaks, or even postponing skiing, hiking, and rafting activities in potentially affected areas are some representative examples. WM planning can become safer as long as the frequency of likely-to-be-exacerbated diseases or the presence of zoonotic disease vectors in the local biota is taken into account. Therefore, WM attempts should be promptly communicated with public health authorities to create contingency plans for WM-associated “adverse events.”

WM has also the potential to benefit health. So far, rain enhancement in the UAE has improved the population’s access to water. Thriving agriculture has also leveraged the living standards of communities that would otherwise face poverty. ^{Reference Munoz20} Similarly, decreasing greenhouse gases can also decrease the burden of asthma, rhinosinusitis, and chronic obstructive pulmonary disease in the course of time. ^{Reference Storelvmo, Boos and Herger9} At a larger scale improving agricultural production, maritime, trade, travel, and transportations by means of WM can contribute to financial growth, part of which can be channeled toward biomedical advances and equitable health care. In the foreseeable future, this can contribute to addressing the global financial effects of coronavirus disease (COVID-19).