In terms of marital status of the population 20 years old and over in 2007, there are 4,841 single or 20.2% of the total population of the age range which is 24,016. There are more single males than females with a ratio of 183 males per 100 females. Sixty percent of those 20 years old and over is married, 8.2% is widowed, 1.6% is divorced/separated, 9.8% is common-law/live-in and 0.2% is of unknown marital status.
A vast majority of households or 98.9% speaks Bikol as language at home. Only 0.88% of households speaks Tagalog at home followed by Bisaya at 0.08%. The people of Irosin are mostly Christian where 96.22% of the total population is Roman Catholic, 1.52% is Iglesia ni Kristo and 0.074% is affiliated with the UCCP. The rest are distributed into different denominations.
In 2007, of the total population of 5 years old and over of 42,923, 26.84% is in elementary grade level, 16.83% is elementary graduate, 15.77% is high school undergraduate, 16.11% is high school graduate, 5.36% is college undergraduate, 5.56% is academic degree holder while only 0.11% has post baccalaureate education. There are more female academic degree holders than male with a ratio of 78 males for every 100 females. The literacy rate of 10 years old and over is 98% in 2015.