Some dictionaries mark the pitch (OS X built-in, 三省堂スーパー大辞林).
はし [0] 【端】
はし [1] 【箸】
はし [2] 【橋】
The number marks which mora the pitch changes on.
Here’s some visualisations (the final empty dot denotes the pitch of a following particle は, に etc)
[Edit: as regards the OP’s question, 人工 and 人口 are both [0], so they would sound the same and context would be the determiner - or the speaker might choose different words to avoid misinterpretation!]