DK History of Britain and Ireland: The Definitive Visual Guide (2011) claims:
17 The average life expectancy in years in Liverpool during the 1850s. High infant mortality depressed the figure, as did the city’s unhealthy cellar dwellings and an influx of famine-weakened Irish immigrants.
Szreter and Mooney (1998) give two sets of estimates:
Szreter and Mooney (1998) started a debate about whether life expectancies fell around the mid-19th century. But even if we use their pessimistic estimates, average life expectancy in Liverpool in the 1850s was 27, not 17. See also Razzell and Spence (2005)