Ink types also vary in their environmental impact, depending on their ingredients, formulation, and application. Generally, ink types can be classified into four categories: petroleum-based, vegetable-based, water-based, and soy-based. Petroleum-based ink is the most common and cheapest type of ink, but it also has the highest environmental impact. Petroleum-based ink contains toxic and non-renewable substances, such as mineral oil, benzene, and toluene, which can harm the environment and human health. Vegetable-based ink is made from renewable and biodegradable substances, such as linseed oil, sunflower oil, or rapeseed oil, which have a lower environmental impact than petroleum-based ink. Water-based ink is made from water and pigments, which have a lower environmental impact than both petroleum-based and vegetable-based ink. Water-based ink does not contain solvents or volatile organic compounds, which can reduce air pollution and health hazards. Soy-based ink is made from soybean oil and pigments, which have the lowest environmental impact of all ink types. Soy-based ink is renewable, biodegradable, and non-toxic, and it also produces brighter and sharper colors than other ink types.