How many people work and live there?
There are many for all ages, whether old or young.
When you arrive in Cambodia, the capital Phnom Penh, You can ask them about the garbage area, They will show the Stung Meanchey area, Most tourists do not visit the area because there is nothing to see, only poor people and the stench of garbage.
But if you want to come and see, you can ride a motorbike or a Khmer trailer around 5usd to 6usd from Central Market to there, if you ride from Russian Market to Stung Mean Chey garbage area take around 15minute spend 4usd to 5usd for oneway.