Background: Medical research on the effects of excessive light on the human body suggests that a variety of adverse health effects may be caused by light pollution or excessive light exposure, and some lighting design textbooks[33] use human health as an explicit criterion for proper interior lighting. Health effects of over-illumination or improper spectral composition of light may include: increased headache incidence, worker fatigue, medically defined stress, decrease in sexual function and increase in anxiety.[34][35][36][37] Likewise, animal models have been studied demonstrating unavoidable light to produce adverse effect on mood and anxiety.[38] For those who need to be awake at night, light at night also has an acute effect on alertness and mood.[39]

Situation: Two friends, John and Abe, worked at the same warehouse. John was exposed to very strong light all the time, while Abe worked in a  more normal environment. John started experiencing health problems after a while.

Question: Which worker was exposed to more light pollution, John or Abe?
Answer: John

Situation: Two friends, John and Abe, worked at the same warehouse. John was exposed to very strong light all the time, while Abe worked in a  more normal environment. John started experiencing health problems after a while.

Question: Which worker was exposed to less light pollution, John or Abe?
Answer: Abe

Situation: Two friends, John and Abe, worked at the same warehouse. John was exposed to very strong light all the time, while Abe worked in a  more normal environment. John started experiencing health problems after a while.

Question: Which worker was influenced more by improper spectral composition, John or Abe?
Answer: John

Situation: Two friends, John and Abe, worked at the same warehouse. John was exposed to very strong light all the time, while Abe worked in a  more normal environment. John started experiencing health problems after a while.

Question: Which worker was influenced less by improper spectral composition, John or Abe?
Answer: Abe

Situation: Two friends, John and Abe, worked at the same warehouse. John was exposed to very strong light all the time, while Abe worked in a  more normal environment. John started experiencing health problems after a while.

Question: Which friend worked in a healthier work environment, John or Abe?
Answer: Abe

Situation: Two friends, John and Abe, worked at the same warehouse. John was exposed to very strong light all the time, while Abe worked in a  more normal environment. John started experiencing health problems after a while.

Question: Which friend worked in a less healthy work environment, John or Abe?
Answer: John

Situation: Two friends, John and Abe, worked at the same warehouse. John was exposed to very strong light all the time, while Abe worked in a  more normal environment. John started experiencing health problems after a while.

Question: Which worker experienced stronger effects on alertness and mood, John or Abe?
Answer: John

Situation: Two friends, John and Abe, worked at the same warehouse. John was exposed to very strong light all the time, while Abe worked in a  more normal environment. John started experiencing health problems after a while.

Question: Which worker experienced weaker effects on alertness and mood, John or Abe?
Answer: Abe

Situation: Two friends, John and Abe, worked at the same warehouse. John was exposed to very strong light all the time, while Abe worked in a  more normal environment. John started experiencing health problems after a while.

Question: Which worker experienced more adverse effects on mood and anxiety, John or Abe?
Answer: John

Situation: Two friends, John and Abe, worked at the same warehouse. John was exposed to very strong light all the time, while Abe worked in a  more normal environment. John started experiencing health problems after a while.

Question: Which worker experienced fewer adverse effects on mood and anxiety, John or Abe?
Answer: Abe