###### Abstract
It states that there are increased safety risks, such as damage to signals, which can lead to dangerous situations, such as derailments, and these incidents can result in delays or cancellations of services. All these factors contribute to the increased operational and legal costs associated with dealing with vandalism and graffiti in the rail sector. [18]. The economic impact of graffiti interventions on trains extends to all cities around the world. The magnitude of the associated costs is not only linked to the number of cases, but also to the strategies implemented for prevention and clean-up. Taking the Spanish transport operator Renfe as an example, in 2018, it spent EUR 15 million on cleaning up its fleet, removing 4000 graffiti acts [19], equivalent to the purchase of three trains [20]. However, by 2020, the costs amounted to EUR 25 m [20], marking an increase of 166%. Catalonia (the autonomous Spanish community) incurred expenses of EUR 6.5 million in 2021 alone to combat graffiti, affecting almost 80% of the trains in circulation. [21]. The persistence of the problem led Renfe to normalize, in 2023, a large contract of almost EUR 40 million for the provision of graffiti removal and cleaning services [22]. This situation is not unique to Spain, as other countries such as Belgium, the Netherlands, Germany and Australia also face similar challenges. Brussels, the capital of Belgium, allocated EUR 4.2 million in 2018 to remove graffiti from its train fleet, a figure that increased to EUR 6.15 million in 2020 [23]. In the Netherlands, spray interventions represent an annual investment of EUR 10 million. In Berlin, the capital of Germany, EUR 10 million is spent annually, according to the BVG Berlin [24]. In Australia, Sydney Trains New South Wales faces an annual expenditure of EUR 30 million to remove graffiti from its rail fleet [25]. This situation reflects a common challenge faced by rail authorities around the world. One of the main problems we identified is linked to the method of cleaning. Currently, the main methods of graffiti removal in the railway industry are mechanical removal (brushes, scrapers, and scouring pads) and chemical cleaning (solvent mixtures of hydrocarbons, ethers and/or alkalis). They are sometimes combined or complemented to ensure satisfactory recovery of trains. Generally, the remover is applied by spraying or depositing it with a brush. It is left to act for the time stipulated by the manufacturer. It is then removed by abrasive methods such as brushes or pressure jets and cleaned one last time with soap and water. Finally, a hot water rinse is applied to the entire carriage [26]. However, chemical removal methods may yield unsatisfactory results, requiring repainting or re-striping of the convoys. According to some authors, this problem may be aggravated by the colour of certain aerosols, such as red and blue, which are difficult to remove, causing losses and unsatisfactory results, making it necessary to propose another type of treatment [27]. In addition, the effect on the health of operators using the chemical methods traditionally used for the removal of graffiti on railway supports has been studied [28]. They were declared as potentially toxic and irritating to the skin, eyes and mucous membranes [29]. The harmful effects on the health of workers related to the chemical composition of the solvent mixtures are as follows [10; 28; 29]:  
* Ethylene glycol ethers: May affect reproductive functions and the respiratory system. Penetrate through the skin. * Limonene: May cause eye irritation and alteration of the respiratory tract. Dermal disorders. * Methyl ethyl ketone (MEK): may cause headaches, eye irritation, respiratory impairment and may impair cognitive functions, e.g., causing a loss of balance. * Methylene chloride: This is an irritant carcinogen that may cause eye irritation, impaired respiratory tract and cognitive functions, such as loss of balance. Prolonged exposure may cause liver and kidney damage or changes in the blood's ability to carry oxygen.