Lead water pipes.
In the house where I grew up (council), we had lead water pipes. In the morning we had to run the water for a few minutes to get rid of most of the poison which had accumulated during the night. Seems quite shocking to think of now and I wonder what effect it had on us at the time. Maybe that's why the summers seemed so nice; we were all stoned on lead (don't try this at home kids).
Now, lead pipes are illegal, so the government puts flouride in the water instead.
