{'acid rain': [1, 0, 2, 3], 'air pollution': [5, 0, 0, 3], 'carbon monoxide': [3, 0, 1, 1], 'carbon dioxide': [2, 0, 5, 6], 'sulphur dioxide': [0, 0, 0, 1], 'methane': [0, 0, 0, 5]}