Poisonous mould
From Tardis Wiki, the free Doctor Who reference
As part of the Committee's plans, a poisonous mould was put into Cardiff Bay and the reservoir. Ng and St John Colchester were made aware of it whilst Tyler Steele was homeless (AUDIO: Hostile Environment) and Bethan Foster mentioned it as an excuse to replace the water containing retcon at the inquiry. (AUDIO: A Mother's Son) On Day Zero, Cardiff lost its water supply. Ng and Mr Colchester found that the mould was quick to multiply. (AUDIO: Day Zero)
