The phrase "where it affects" is correct and can be used in written English.
You can use it when referring to the potential consequence of an action or situation. For example, "We must be careful in how we utilize this technology, where it affects our environment."
This is particularly challenging where it affects the core businesses of companies.
High soil pH is a serious agricultural problem in northern China, where it affects apple metabolism, specifically root development.
At this time of year it moves south of the equator, where it affects parts of Australia.
A strong identity and in-house government allow students to participate in the decision-making process where it affects them most directly -- in their own living groups.
Human influence on the Earth System and hydrologic cycle has reached the point where it affects the hydrologic balance between ocean and continental storage reservoirs.
Glaucoma occurs with increasing frequency in people over the age of 40 to the point where it affects about 2 to 3percentt of people 65 and older.
They were preoccupied to the point where it affected their performance.
The disease was first identified in the USA in the 1980s, where it affected greyhounds.
As a result, a train that was well behind schedule where it affected the greatest number of riders could still arrive within the five-minute window.
Between 2000 and 2012, adult obesity has shown a steady upward trend in the capital, where it affected 16% of the city population in 2000, 19% in 2006, and 26% in 2012.
The attack was an embarrassing blight on Target's reputation, coming shortly after the busy holiday shopping season, where it affected a record number of customers.
