Question: Why is the blue lagoon dangerous?

Laura Hunt answered on 7 Jul 2020:

Hi Samuel, thank you for your question – it is a good one! The water in the blue lagoon, in Derbyshire is dangerous for us to swim in, because it has a very high pH, close to that of bleach! The water is very alkaline (the opposite of an acid, similar to bleach or ammonia), and this can cause irritation to our eyes and skin, as well as making us feel poorly. The blue lagoons water is particularly alkali (more so than other bodies of water) because the lagoon is right next to an old mine. A chemical called calcium oxide was left behind in relatively high concentrations in the old mine, and is washed into the lagoon by rainwater. This chemical compound is what makes the lake water so alkaline.

I have also seen a couple of reports of old cars and dead animals in the blue lagoon, which are likely to also pollute the water with unpleasant chemicals. There are much other nicer places in the UK to swim, so I would definately avoid it!