Q.
What Is a Toxicity Rating (PEL, TLV, AEL)? Which Solvent Is the Safest (Has the Least Toxicity)?
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A.
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At MicroCare, we recommend you start improving safety by improving your cleaning processes, which means you should work at creating an environment where people use less solvent. MicroCare recommends using the Trigger Grip™ dispenser (photo, right). That way, no matter  which solvent you select, you will always use less solvent, get less on your hands, less in your lungs, less in your eyes. In this case, less is more -- much, much more.
Micro Care Uses Independent Toxicity Ratings
Now, the next step is to use safer (less toxic) chemicals. In the solvent world, chemists measure safety in terms of toxicity ratings. These usually are called TLV ("Threshold Limit Value", PEL ("Personal Exposure Limit"), AEL ("Assigned Exposure Limit") or similar terms. These terms are generally (but not exactly) synonymous, and all of these rating systems work in the same manner.
The best safety ratings are called TLV ratings are can only be assigned by the independent safety organization ACGIH. These toxicity ratings are based on data derived from very systematic testing protocols on animals. The actual lab results are then adjusted by trained hygienists and toxicologists to simulate a constant exposure to the solvent for eight hours per day, five days a week, for a hypothetical thirty-year working career.
Toxicity ratings are expressed in parts per million of chemical exposure. Like bowling, a high score is better. It means you can be exposed to more of the chemical without any adverse effect. A lower score means even a brief exposure to the cleaner may pose health hazards.
(As a bit of background, thirty years ago the most popular CFC-based cleaner was given a TLV of 1,000 ppm. Most people feel if the same tests were done to today's more demanding specifications the safety ratings would have been about half of that. In addition, it should be acknowledged that none of the cleaners sold by MicroCare are even close to being as toxic as smoking a cigarette. It's important to keep these risk factors in perspective.)
A "Rule of Thumb" About Toxicity Ratings
Here is a good rule of thumb. Toxicity ratings of over 400 ppm would be generally safe under most industrial situations. Ratings from 100-400 ppm should require the product to be managed carefully. Ratings under 100 ppm are generally "pushing the envelope" and those chemicals should be used with caution.
It goes without saying that "toxicity" is NOT a perfect description of safety. Other important factors, such as flammability, storage, handling and disposal, need to be included in any safety analysis. Before selecting a solvent, contact a safety expert if you are unfamiliar with these issues and worried about the implications. Whenever the data is available, MicroCare uses ACGIH toxicity ratings. When that data is not available, MicroCare uses the toxicity ratings assigned by the solvent manufacturer. If that is not available, MicroCare lists all the toxicity data on the ingredients of each solvent within the MSDS sheet.
Whatever solvent you select, you should use gloves and other protective clothing if there is any risk of skin or eye contact. There is a very good web site which has excellent technical data about the huge array of glove choices available on the market. It's organized by the Office of Radiation, Chemical and Biological Safety (ORCBS) of the Michigan State University, so it's not tied to any one manufacturer or brand. When you identify a chemical it suggests the best type of glove to use. In the color chart, you're looking for gloves rated in white or green. When selecting gloves, check the MSDS sheet to get the EXACT chemical name or CAS number for the solvent you are using; different solvents require different types of gloves.
As a general rule for MicroCare products, Viton® gloves work adequately. In some applications a more durable two-part glove might be necessary. Chose the powderless option if it is important to control nonvolatile residues in your production process. These are widely available from quality distributors everywhere.
If you don't have time to go to the ORCBS site, then select the best impervious gloves and protective clothing you can find if there is any risk of skin contact. Gloves, splash goggles, aprons (when handling open drums) and safety shoes with steel toes are highly recommended.
MicroCare Has Good Solvent Choices with Low Toxicity (High TLV Ratings)
Isopropyl alcohol, also called rubbing alcohol, is a good benchmark. Super-pure, anhydrous IPA is available from MicroCare under the IsoClean™ brand name (#MCC-BAC). It has a TLV of 400 ppm and a familiar aroma. While it is not a very powerful cleaner, it certainly isn't going to make anyone sick.
If you like alcohol cleaning, we recommend ProClean™ (#MCC-PRO) which is a blend of three alcohols. It offers stronger cleaning than IPA with an improved safety rating of 568 ppm.
VeriClean™ (#MCC-DC1) has a TLV of 200 ppm which sounds a bit on the low side, but in this case the TLV doesn't tell the whole story. VeriClean™ is a remarkable solvent, produced by Dow Corning, and it is highly effective on most fluxes and pastes, even "no clean" technology. This cleaner is a siloxane-based chemistry so it is distantly related silicone. It is unique in that the raw material is quartz, also known as sand. (Yep, we mean S-A-N-D, as in high tide, sunburn and beach blanket bingo.) So Dow Corning does their magic and you get a versatile cleaner with the best environmental pedigree on the market. As for safety, the MSDS sheet for the raw material says "No first aid should be required." You don't get much safer than that.
The HFC solvents from DuPont (Flux Remover C (#MCC-FRC), SuprClean (#MCC-SPR), PowerClean (#MCC-PW2) and so on) have very good toxicity ratings. Most of them have assigned TLV ratings in the range of 200 ppm. But in addition to being relatively safe they also are nonflammable. They dry quickly, have very little odor, have excellent materials compatibility profiles and most of them can be used in heated cleaning systems.
MultiClean™ (#MCC-MLCW) may be MicroCare's safest solvent, with a computed PEL of 1,000 ppm. It is an excellent choice for cleaning "no clean" residues and any water soluble contamination. Unfortunately, MultiClean™is a tightly-targeted solvent and is not effective on a wide range of contamination. It is very inexpensive, but it also dries more slowly than many engineers would like. MultiClean™is only available in bulk packaging and in presaturated wipes.
Specific details about each product and its toxicity ratings can be found on the second page of every product specification sheet, and in every material safety data sheet (MSDS), as published in this site.
Updated 8-11-2008
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