For the last several decades, ecologists have known that heavier stable isotopes become more enriched in a consumer than in the food they eat, and have agreed that they increase by a standard additive factor
of 3.4 parts per thousand in the consumer.
The associated infection can also act as an additive factor
, hastening the erosion of the urethra and surrounding skin.
Gilmour at the Benedict (Md.) Estuarine Research Laboratory -- tended to have an acidic pH, Rudd says it's possible that sulfates may represent yet another additive factor
contributing to the methylmercury problem in regions beset by acid rain.
After traumatic brain injury there is additive factors
that affect the motor function in these patients.