Around 3 months ago I decided to take the more environmental route and stopped drinking bottled water in favour of filtered tap water. I don't drink tea, coffee, soft drinks etc., it's exclusively water so I get through at least 1.5-2L daily.
In the last few months I have also noticed a very pronounced decrease in my libido but I didn't immediately link the two. Then, by chance, I happened on an article about Estrogen in tap water. This is due to being contained in high levels in female urine (due to the pill) and out of date contraceptive medication being flushed down the toilet. It appears lots of pharmaceutical drugs end up being pissed back into the system and are not removed by water treatment.
Here's an article from the New Scientist:
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It's based on the US, but I suspect the UK is very similar. It claims the levels of chemicals are safe, but I can only go from my own personal experience.
The upside is I have cut down on my use of mansize tissues and my partner's sphincter has regained some elasticity. But I'll be honest, I preferred having a higher sex drive and think I'll be going back to bottled water pretty soon. So, if it means the planet has to die so I can get back to wanking 3 times a day, then thats the way it'll have to be.