Leyden: According to hundreds of studies that have been done by various investigators as well as the manufacturers themselves, the materials that constitute disposable diapers appear to be very safe. In fact, more than 400 studies were performed specifically on the superabsorbent material. This is comparable to the number of studies the FDA requires to approve a new drug and far more than it requires to approve a medical device. In addition, there have been many studies of effects on animal and human skin. I've been involved in some of them, looking at the irritation potential as well as the true allergic potential of superabsorbent material. Again, no harmful effect has been demonstrated. That is despite applying the superabsorbent in both wet and dry forms to skin - both intact skin and skin where the stratum corneum has been breached by scarification as I described earlier. The diaper manufacturers do occasionally receive consumer inquiries on superabsorbent gel beads that sometimes escape from the diaper and appear on the skin. A large number of human studies have shown that these gel beads are safe for skin contact and cause no harm. Finally, there have also been many tests both in animals and in humans on the superabsorbent material's ability to induce immunologic reactivity, and again no harmful effect has been observed. These results correlate with the experience of parents and their doctors that disposable diapers do not cause irritation or true allergic sensitization.
Spraker: How about mutagenicity or genotoxicity tests? That would refer to chemical effects that might induce changes in germ cells, possibly leading to genetic diseases, and in somatic cells, possibly leading to carcinogenesis. This would include DNA damage in one or a few DNA pairs, or mutations in the genes themselves, such as breakage, rearrangements, or changes in number.
Leyden: Those possibilities have been assessed in more than 50 independent studies. No mutagenic or genotoxic effects were seen. If any had been seen, the manufacturers would not have proceeded with development and incorporation of superabsorbent material into these products.
Spraker: Dr. Schuman, can you comment succinctly on ingestion and inhalation?
Schuman: Yes. Again, many studies have shown that the ingestion of superabsorbent material is not harmful. So we don't need to worry about this material because it's been well demonstrated to be perfectly safe, even if accidentally ingested.
Spraker: But since the superabsorbent material absorbs water and swells, wouldn't it swell in the intestine if a child swallowed some of the gel material?
Schuman: The polymer particles in the diaper do swell. The particles in this material are 400 to 800 microns in diameter when dry, about the size of common table salt. They swell to three to four times that size when wet. But they don't stick together to form a mass. Studies done with animals showed the gel beads pass right through the gastrointestinal tract like little discrete beebees. In addition, oral feeding studies for toxicologic assessment were done with rats in which superabsorbent material was added to their food in a dose of 3 grams per kilogram of body weight per day for 93 days. That would be the equivalent of a child consuming an entire diaper every day. The only effect was some softening of the feces.
Spraker: What about possible exposure by inhalation to babies or their caretakers from using disposable diapers?
Schuman: That was also looked at in simulated diaper-changing studies. In several separately conducted studies, technicians changed 1,000 diapers on baby mannikins in 8 hours while the air quality was evaluated. Even under these highly exaggerated conditions, no breathable particles were found in the air.
Spraker: Dr. Krafchik, can you comment on the impact of disposable diapers on the environment?
Krafchik: As far as public safety is concerned, I think it's been shown that disposable diapers don't have any harmful effect. No toxicity has been demonstrated in the landfill sites where they're disposed of. The manufacturers have been quite sensitive to environmental issues because of the early public concern about nonbiodegradable waste.
Spraker: In the past there has been concern about the sheer bulk of the diaper material going into landfill.
Krafchik: Numerous life cycle assessments were done in the 1980s and showed that disposable diapers did have an environmental impact but that alternative products also had comparable environmental impacts. If you use cloth, for instance, you have to use hot water, strong detergents, and energy for drying, thus depleting natural resources. Today, since there's less bulk to diapers and less packaging, there's less material needing disposal. But manufacturers continue to work at reducing raw material usage and at making the manufacturing process less energy intensive.
Spraker: What about the possibility of recycling some of the materials?
Krafchik: In the late 1980s and early 1990s, there was some effort on the part of the manufacturers to recycle materials, but ultimately this was not feasible financially. Today, most solid waste in the US goes into landfill, including diapers, which have been estimated to be about 1% of the total landfill volume. The superabsorbent material, however, actually has other uses. It could be recycled for horticultural applications, for example.
Spraker: Such as water trappers to add to your potted plants so that you don't have to water them as often?
Krafchik: Yes, because the material holds water and gradually releases it. There are studies that have shown there's no toxicity to soil organisms and that the material doesn't migrate into the ground water. It would be perfectly safe for the superabsorbent polymer to be present in soil and compost. However, superabsorbent contaminated by feces would have to be sterilized first.
Schuman: Are there any other components of disposables that could be recycled?
Krafchik: You could recycle the plastic components, but it takes time and energy to separate, collect, and recycle them.
Schuman: So therefore it would not be cost effective. However, diapers could be considered as a potential power source. Plastic is derived from a fossil fuel, so you should be able to recover energy from it. But waste-to-energy incinerators haven't taken hold in the US because of the "not in my backyard" syndrome. That's done mostly in countries such as Japan, where they have no place to put solid waste. It can be done if the culture or society deems it necessary.
Spraker: What about somehow making the diaper dissolvable so that it could go through the plumbing? That's where other fecal waste goes to get processed.
Schuman: The technology is not available yet to give us a good flushable top sheet and liner. The problem is that you would want it to disintegrate when it hits the water in the toilet but you wouldn't want it to disintegrate when urine hits it. In addition, diapers need to have a good shelf life. In some places diapers can be on the shelf for a year, enough to be affected by high humidity.
Spraker: So, to summarize, one of the other major concerns of the public is the environmental impact of disposable diapers. Studies have shown that any negative environmental impact they might have is comparable to that of the alternative diapering methods. Importantly, manufacturers have been working to reduce this impact by making diapers that use less material yet perform better.