The Acid SnowA combination of industrial pollutants and ozone depletion causes the global atmosphere to become highly caustic, resulting in "acid snow" that burns exposed skin and requires perpetual outdoor shielding.The novel is set in a future where almost all human activity takes place in tunnels and subterranean networks.They must venture to the surface in a cumbersome "exposure suits" to make repairs or acquire resources, fearing the constant threat of suit failure and contact with the toxic snow.