Выдержка из MSDS для лимонной кислоты:
"Carcinogenicity
IARC:No component of this product present at levels greater than or equal to 0.1% is identified as probable, possible or confirmed human carcinogen by IARC.
ACGIH:No component of this product present at levels greater than or equal to 0.1% is identified as a carcinogen or potential carcinogen by ACGIH.
NTP:No component of this product present at levels greater than or equal to 0.1% is identified as a known or anticipated carcinogen by NTP.
OSHA:No component of this product present at levels greater than or equal to 0.1% is identified as a carcinogen or potential carcinogen by OSHA."
Так что нет, не является.
Каждую секунду в вашем организме в ходе цикла трикарбоновых кислот образуется и тратится лимонная кислота. Вы б ещё спросили, канцерогенна ли вода.