 In some areas of the world, including Berlin, Germany, dropping salt is prohibited altogether except on the highest-risk roads; plain sand without any melting agents is spread instead.While this may protect the environment, it is more labour-intensive, as more gritting runs are needed; because the sand is insoluble, it tends to accumulate at the sides of the road, making it more difficult for buses to pull in at bus stops.Grit is often mixed with hydrous sodium ferrocyanide as an anticaking agent which, while harmless in its natural form, can undergo photodissociation in strong sunlight to produce the extremely toxic chemical hydrogen cyanide.