Health Secretary Manuel Dayrit said swimming or wading in polluted waters could cause various skin diseases like fungal infection, dermatitis and scabies.
Dayrit added that eye infection, leptospirosis and diarrhea could also be acquired from dipping in the waters of Manila Bay, where dead fish were found recently.
The cause of the fishkill is still unknown, but the sudden change of climate and pollution are the likely causes. The possibility that the fish were poisoned was not ruled out.
It has become a common practice for many Metro Manila residents to go swimming in the bay when the summer season comes.
A report from the Department of Environment and Natural Resources (DENR) showed that when water samples from the bay were tested in 2003, they exceeded the acceptable fecal coliform limit of 200 most probable count per 100 milliliter (mpn/100 ml) of water.
The water specimens taken from the Navotas Fish Port station yielded as high as 50,075 mpn/100ml.
The DENR also reported that the Manila Bay does not meet the safety criteria for swimming.
The agency maintains 10 monitoring sites in the bay to monitor the pollution level, namely: the Navotas Fish Port, Luneta Park, Bacoor and in seven resorts in Cavite — Lido Beach Resort, San Isidro Beach Resort, Villamar Beach Resort, Celebrity Beach Resort, Punta Grande Beach Resort, Garden Coast Beach Resort and Costa Euginio Beach Resort.
The pollution in Manila Bay is attributed to the sewerage facilities and presence of squatters on its shoreline.