Excess Winter Mortality in England and Wales

When deaths in England and Wales for the period December to March are compared to the average of deaths occurring in the preceding August to November and the following April to July an excess winter mortality is found. The first graph, from a release by the UK Office of National Statistics shows the trend in excess winter mortality since 1950.
Disease of the respiratory system, and secondarily the circulatory system are identified as the main causes of excess winter mortality.
The data used by the ONS isn't available further back, but statistics from FreeBMD can be used to show a longer term trend back to 1838.  For each year I used the first quarter for the winter mortality and third for summer. Points are annual figures, the blue line the six year moving average and the red line the six year average for the period covered by the first graph.
The most notable feature is the higher mortality in the 20th century which persists even when the growth of population is factored in.

Could it be the result of increased coal combustion as the nation became more wealthy? Is the drop following the pea-souper fogs or the early 1950s connected to coke, and then gas replacing coal? Statistics on domestic coal consumption, millions of metric tonnes, reflect the same trend.

Deaths in the years of high excess winter mortality 1951, 1929, and 1919 were dominated by influenza and pneumonia.
Three of my grandparents died in January or February. Were they victims of coal?