Hi all... I have actually have a lot of questions in my mind, but for now just wanted to ask one of them. We recently started laying the groundwork for EMS towards ISO 14001 and started from the process where we use most of the chemicals. Now, let's say we have electrolysis unit. Inputs include Chromic Acid and Sulfuric acid. Since, from my understanding, we have to consider both inputs and outputs of this electrolysis process I identified Chromic Acid and Sulfuric Acid as Environmental aspects (inputs). I used MSDS pages to identify their potential impacts on Air, Water, Land as well as their impacts on humans under the headings of inhalation, dermal and oral (acute and chronic). To assess exposure severity and frequency we prepared a spreadsheet including the chemicals' daily usage, how many times they are used and how long is exposure (how many minutes they are used in a day). On the same spreadsheet we added columns for potential exposure pathways for humans and for environment (air, water, land) and personal protection equipment in use. For Example;

Process:
Electrolysis

Aspect:
Chromic Acid

Amount used: 20 kg/2 months 33,33 gr/day (divided amount to 60 days)

Exposure time: 3 min. (for each use)
Frequency of use: 30 times/day (average)

PPE: Mask with P3 type filter, Chemical Safety goggles and apron and gloves

Exposure Pathways:
Humans: Inhalation
Environment: Indoor air, water (in case of massive container breakdown)

and we used three columns to rank for workers, society, environment

My question is: When we rank impacts and exposure, how do we rate them? We decided to use a scale 1 to 5 (1 being lowes and 5 being highest).when group rates the potential effects how do we determine if the impact or exposure is low risk or medium risk or high risk? Is it all judgement based or is there a way to make the rating more objective like setting some numerical criteria and rating according to that? Any and every help would be greatly appreciated.

is there a way to make the rating more objective like setting some numerical criteria and rating according to that?

That's a good way to go. Don't fret too long over the categories and/or the scale. As long as you apply the same criteria and rating process to all your aspects, the most significant should rise to the top of your listing.

The process we used to determine SEA's was much like performing a PFMEA.