Science / Medicine : Not Clean Enough : Quest for a Risk-Free Compound Remains Frustrating
Silk dresses, printed circuit boards, and greasy nuts and bolts all have something in common. They are cleaned with environmentally unsound chemicals. But scientists are trying to change that.
Now that cleaning agents face stringent governmental regulation, industry must find alternatives or vanish along with the chemicals it depends upon. Ideally, the replacements would be safer than their predecessors.
Unfortunately, the sought-after risk-free compounds simply don’t exist. Every new chemical introduced has drawbacks of its own. These alternatives either don’t perform as well or present new hazards.
A few products readily available on the market are alternatives to chlorofluorocarbons (CFCs), the substances that deplete the ozone and that are being being phased out over the next decade.
One is d-limonene, a compound derived from citrus peel. D-limonene belongs to a class of chemicals called terpenes, which are produced by a host of plants--pine and citrus trees in particular.
Terpenes have been used for years on a small scale in cleaning products such as Pine Sol. During the mid-’80s, the Florida-based company Petroferm began marketing terpene-based products as alternatives to CFCs for use in cleaning printed circuit boards and other metal parts.
At first glance, terpenes seem like ideal alternatives. Petroferm emphasizes the environmental benefits of a product that is derived from a natural source. Michael Hayes, director of electronic and specialty chemicals at the company, says the product is so safe it can be flushed down the drain. “Anything made by every green plant in the world,” he says, “must be biodegradable.”
Recently, however, the Office of Toxic Substances of the Environmental Protection Agency began testing d-limonene. The OTS studies indicate that d-limonene is relatively toxic to freshwater fish. In addition, based on rodent tests, it appears d-limonene may also be toxic to the liver.
Why is it safe to eat an orange and potentially hazardous to work with d-limonene? The d-limonene in orange peel is tightly bound to other chemical components, making it impossible for the body to absorb. In addition, a single orange contains only a tiny quantity of the chemical as opposed to the high concentrations found in a vat of the pure compound.
“Simply because something occurs naturally doesn’t necessarily let it off the hook, “ said Katy Wolf, head of the nonprofit Institute for Research and Technical Assistance. Currently there are no restrictions on the use of terpenes. Petroferm began selling its first terpene-based cleaners in 1985. Today it has more than 200 customers, AT&T; among them.
Another product being tested is DGBE, a type of glycol ether. DGBE is used as an additive to water for cleaning metal parts and circuit boards. As far as DGBE’s safety is concerned, the jury is still out. Only limited studies have taken place on that specific compound, but according to the OTS, some of the glycol ethers cause birth defects.
The chemical is currently being marketed as a safe replacement for chlorofluorocarbons. One distributor markets the DGBE additive as a non-hazardous, biodegradable cleaner.
What concerns Wolf and others is that products can be marketed for several years before they are adequately tested. “In the past we moved from one chemical class to another,” she says, “without taking into account what we were doing. We’re suffering the consequences of that now and I’m frightened we’re going to do that exact same thing again.”
The EPA, which holds the regulatory gavel, acknowledges that trade-offs come with every substitution. “You can’t substitute one bad actor for another,” says Diana Locke, toxicologist with the OTS. “What you need to do is weigh your troubles.”
The agency was forced into this balancing act when it was simultaneously hit by two recent pieces of information. First, new studies on global warming indicated that ozone depletion could be more severe than anticipated.
In addition, one touted CFC alternative, HCFC 141B--reputedly a more benign form of CFC--has not lived up to expectations. When scientists originally calculated the ozone depletion value for 141B, it was substantially lower than the chemicals slated to be banned.
The EPA and industry hoped it could be used as a transition compound, as society weaned itself from CFCs. It turns out 141B could deplete the ozone more than one chemical on the forbidden list. Nevertheless, agency plans to proceed with the chemical remain unchanged.
“I think that the . . . EPAs around the world are grappling with the issue,” said Stephen Andersen, director of technology transfer and industry programs with the EPA. “They are trying to come up with prudent business advice and prudent environmental protection at the same time. It’s not very easy.”
Some members of the industrial community believe the EPA’s previous actions are returning to haunt the agency. Paul Cammer, president of the Halogenated Solvents Industrial Alliance (HSIA), an organization representing producers, distributors and users of cleaning solvents, believes the EPA acted precipitously when it banned methyl chloroform, a ubiquitous solvent with a relatively low ability to deplete the ozone. The ozone-depleting potential for methyl chloroform is lower than that of HCFC 141B. But now methyl chloroform is being phased out while HCFC 141B is about to make its debut.
“There is no perfect solution,” Cammer says. “There are trade-offs. And when we ban something, we’d better make sure we understand what those trade-offs are. I don’t think we have done as good a job on methyl chloroform as we should when making public policy decisions. Maybe the times dictated that we weren’t going to take that time . . . but that’s not the way we should do business in the future. We need to understand the risks.”
Aside from specific chemical substitutions, such as replacing CFCs with terpene cleaners or HCFC 141B, industry is wrestling with broader dilemmas, opting for substances that don’t pose obvious hazards yet present new problems. The point is clearly demonstrated by companies using water as a cleaning agent to replace ozone-depleting solvents.
Ostensibly, what could be more benign than water? The catch is that water, unlike many solvents, doesn’t evaporate quickly. Therefore the circuit boards and metal parts that once dried rapidly on their own now need assistance. The drying process requires energy--or burning of fuel--which contributes to global warming. It’s a Catch-22 that only becomes more complicated.
Sometimes water alone won’t do the job and requires special additives formulated for the task. A long list of such chemicals have entered the market. Some of these, such as glycol ethers, have questionable reputations.
No product will ever have a perfectly clean slate, experts agree. As Locke says, “Nothing that cleans is going to be without toxicity. The whole fact that something cleans means it has some toxicity, even soap. There is nothing out there that is going to clean metal parts or circuit boards without some level of toxicity, other than using your own hard labor and water or going back to pounding the rocks and sand. The point is how much and how bad will the exposure be. Because when you combine toxicity with exposure you get risk, and it’s the risk that we’re looking at.”
Wolf agrees with Locke’s assessment. “I’m not sure that I want to prevent things from being used,” she states emphatically. “I want them to be used properly. But unless you acknowledge what the problems are you can’t use (products) properly.”
Chlorofluorocarbon Use
Chlorofluorocarbon were developed in the late 1920s for use in refrigeration systems. Today, CFCs are used across the globe as industrial solvents, cleaning agents and in foam insulation and aerosols. But when released into the atmosphere, the CFC reaction with the ozone layer helps to destroy it. Here is a look at world CFC use, by category, in 1986: Others: 7% Solvents: 16% Refrigeration: 25% Foams: 25% Aerosols: 27% Source: Environmental Protection Agency
