rather than on property owners. The boroughs had the power to create Boards of Health, charged with initiating the reforms, and also empowered to intervene and remove a broad range of "nuisances" to public health. The weakness of the 1848 Act was that it did not compel the boroughs to act, but merely provided the framework for doing so. More comprehensive and forceful legislation was passed by Parliament with the Public Health Acts of 1872 and 1875. The last Act compelled the boroughs to provide adequate drainage, required all new housing to be built with running water, and required all streets to be equipped with lighting and pavements. The boards of health were replaced by urban sanitary authorities overseeing new urban sanitary districts. These authorities were more comprehensive than their predecessors, equipped with teams of medical officers and health inspectors who ensured food safety standards were met and actively prevented outbreaks of disease. Pollution Fog Atmospheric pollution caused by burning cheap soft coal created the city's notorious pea soup fog. Air pollution from burning wood or coal was nothing new to London – complaints about the city's dirty atmosphere exist as far back as the 13th century – but the population explosion and industrialisation of the 19th century aggravated both the severity of the fogs and their lethal effects on Londoners. The fogs were at their worst in the month of November, but occurred frequently throughout the autumn and winter. Sulphur dioxide and soot emitted from chimneys mixed with the natural vapour of the Thames Valley to form a layer of greasy, acrid mist that shrouded the city up to 240 feet (75 metres) above street level. Its most common colour was a greenish-yellow "pea soup", but it could also be brown, black, orange, or grey. At their worst, the poor visibility caused by London fogs could halt traffic and required the street lamps to be lit all day. Conditions for pedestrians were extremely dangerous: in 1873, nineteen deaths were attributed to accidental drowning from victims who fell into the Thames, canals, or docks during foggy weather. There were also increases in crimes like theft, rape, and assault on London streets because of the cover provided by the fog. Charles Dickens Jr. described the "London particular" in his Dictionary of London of 1879: There was wide awareness of the deleterious health effects of extended fogs in London, particularly upon those