Clearing the air on ethanol | A nano Trojan horse | Perfume, perfume

Environmental t News Clearing the air on ethanol

of growing plants for ethanol. Biofuels such as ethanol “simply have not been well studied yet,” says Mark Delucchi, a transportahen Mark Jacobson heard burned. tion analyst at the University of a venture capitalist tout The result: more ozone and California, Davis. With regard to ethanol fuel as a soluabout 185 more deaths per year climate, “We really don’t know even tion to air pollution last year, he across the U.S., with 125 of those the sign of the impacts, positive or was surprised—and intrigued. Jain Los Angeles. Jacobson studied negative,” he says. cobson, an atmospheric chemist at that city in depth because of its While research continues, ethaStanford University, knew that air ongoing smog problem and found nol production is ramping up. The quality got worse during Brazil’s that it has the right atmospheric U.S. Department of Agriculture’s big ethanol push in the latest projections show 1970s and that the reason corn planting skyrocketing was still unclear. to more than 90 million As he soon learned, acres this year, 15% higher many of ethanol’s backthan last year and the most ers are now pitching it as since World War II. a clean-burning, healthy Even more could be alternative to gasoline, in coming. In January’s addition to promoting it State of the Union adas a homegrown fuel with dress, President Bush anpotential CO2 savings. nounced plans to reduce The idea is that ethanol gasoline consumption by burns cleaner than gas, 20% in 10 years, and ethamaking fewer unhealthy nol is a keystone in that emissions and creating plan. E85 works only in New ethanol fuels may worsen smog over Los Angeles. less smog. President Bush, flex-fuel vehicles, of which biofuels industry groups, and even chemistry to make the ethanol there are at least 6 million on U.S. the American Lung Association of switch particularly problematic. roads. E85 pumps, however, are the Upper Midwest have promoted Previous studies have estimated concentrated in the upper Midethanol as good for public health. the pollution and health effects of west, close to the corn. Jacobson decided to use his soburning ethanol, but Jacobson says California’s Air Resources Board phisticated air-pollution model those researchers simply scaled (CARB) is studying ethanol as part to put ethanol to the test. Would up tailpipe emissions and plugged of Gov. Schwarzenegger’s executive switching the U.S. fleet to white those numbers into outdated fororder calling for 10% less carbon in lightning make the country mulas to calculate ozone changes fuels by 2020. But the state is not breathe easier? and cancer rates. His atmospheric yet rolling out the red carpet for His results, published in this ismodel, called GATOR-GCMOM, ethanol. CARB applied for a waiver sue of ES&T (pp 4150–4157), show accounted for the transport of of the U.S. EPA’s rule requiring 10% that ethanol is no silver bullet for tailpipe emissions across the U.S. blends of ethanol during winter health. Switching to E85 blends along with chemical transformamonths and says it’s considering (85% ethanol, 15% gasoline) could tions in the atmosphere—key comethanol’s effects on air quality. result in slightly higher ozone-reponents that had been neglected Rushing ahead to fix one problated mortality, hospitalization, in previous studies. lem can create another, cautions and asthma (9% higher in Los AnThe findings suggest that ethaHadi Dowlatabadi of the Univergeles and 4% higher in the U.S. as nol cannot be promoted simply sity of British Columbia (Canada). a whole), the study finds. Cancer as a boon to public health, JacobIn a previous ES&T study, he found rates would be similar for gasoline son adds. Other factors need to be that a U.K. policy designed to reand E85. studied and weighed before ethaduce carbon emissions created airCompared with gasoline, ethanol use is made widespread, he quality problems by encouraging nol tends to produce less benzene says, such as greenhouse-gas emisparticulate-spewing diesel vehicles and butadiene, but more acetalsions, U.S. dependence on foreign (2007, 41, 387–392). dehyde and formaldehyde, when oil, and the environmental impacts —ERIKA ENGELHAUPT Mark Jacobson

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3788 n Environmental Science & Technology / June 1, 2007

© 2007 American Chemical Society

News Briefs

sure of the energy consumption and yield of the ethanol production from a one particular source. NEV “may not be the best instrument to evaluate biofuels’ contribution to energy security,” the authors admit in the paper. The amount of fossil fuels used in the ethanol-manufacturing process is an important factor that determines “renewability”. Consequently, they used yet another tool, the net renewable energy value (NREV), defined as the energy content of ethanol minus the total fossil-energy inputs. When fossil-fuel inputs (97.35% of the energy inputs) were taken into consideration, the NREV of cassava fell to 9.15 MJ/L. This value, however, is still greater than that reported for energy costs of cassavaderived ethanol in China (Energ. Convers. Manage. 2006, 47, 13–14). Several features make cassava more advantageous than sugar cane or cane molasses. The tuber is already used as a starch source and for chip/pellet products. It can be grown in any season and can be a year-round source of ethanol. “In Thailand, cassava is the third most important cash crop after rice and sugar cane,” says Gheewala. “Over the past 20–30 years, cassava agronomy research has contributed significantly to the development of improved agricultural practices, Nguyen Thi Thu L an

While most of the world is scrambling after corn and sugar for answers to its renewable energy needs, many developing countries are focusing on a lesser known plant—cassava. New research published in this issue of ES&T (pp 4135–4142) calculates the net energy value (NEV) of cassava and suggests that the tuber would be an efficient source of renewable energy in Thailand. The findings provide a “framework” for policy makers to evaluate whether “ethanol from cassava is feasible and practical,” says study leader Shabbir Gheewala of King Mongkut’s University of Technology Thonburi (Thailand). Although molasses is the current source of ethanol in Thailand, the country already has a cassavaderived ethanol pilot plant, and the government is aiming to build 12 full-scale ones by 2008. Using “scaled-up” data from the existing pilot plant, the authors calculate the NEV of cassavabased ethanol as 10.22 megajoules per liter (MJ/L), an overall positive yield. NEV is a measure of the energy content of ethanol minus the net energy used in the production process. The usefulness of NEV in evaluating an ethanol source is debatable, but with well-defined boundaries and clearly stated assumptions, it can provide a mea-

Pieces of cassava are dried into chips in Chonburi Province, Thailand, before being converted to ethanol.

Big picture on the small

The environmental health and safety impacts of nanomaterials remain nebulous, making it difficult for policy makers to move forward with regulations. A new report from Mark R. Greenwood, former director of the U.S. EPA Office of Pollution Prevention and Toxics, lays out a regulatory road map with pitfalls clearly labeled. Thinking Big About Things Small was released in March by the Project on Emerging Nanotechnologies, sponsored by the Pew Charitable Trusts and the Woodrow Wilson International Center for Scholars. Greenwood considered not only government regulations, testing, and labeling and their impacts on the market, but also the role of private toxicity testing and responsibility. Transparency issues, such as the availability of privileged product data, will come into play, he said.

Flushing pharmaceuticals

Prescription drugs can harm the environment when people flush pills down the toilet or throw them into trashcans. Now, U.S. federal agencies are looking for ways to keep waters drug-free. The American Pharmacists Association (APhA) and the U.S. Fish and Wildlife Service agreed in March to start a public education campaign dubbed SMARxT DISPOSAL, which will feature brochures, a website, and events. Tips include crushing or dissolving pills and mixing them with cat litter or sawdust, using the trash instead of the toilet for most drugs, and talking to a pharmacist. The U.S. EPA has endorsed APhA’s disposal guidelines and is considering rule changes to encourage “take-back” programs to incinerate household drugs.

June 1, 2007 / Environmental Science & Technology n 3789

JUPITERIMAGES

Thailand fuels up with cassava

Environmentalt News such as time and method of planting, intercropping, soil erosion control, and especially, weed control and fertilizing.” The result: Thailand uses less fertilizers and herbicides than China to grow cassava, yet it provides a comparable yield. The study addresses a question that’s of policy interest right now, says Uwe Fritsche at the Institute for Applied Ecology (Germany).

However, the authors’ calculations will remain meaningless without an understanding of their economic relevance, says Fritsche. “We have a lot of solar energy, for example, but it’s very expensive so it does not mean much.” The authors agree. “A general idea about the market dynamics is useful to understand the overall situation,” they report in the paper.

Fritsche also points out the absence of any reference to greenhouse-gas emissions. “Net energy balance is for scientists,” he says. The real economic implications of any biofuel source remain unknown without an estimate of its greenhouse-gas emissions, because that is where “most of the current debate” lies, Fritsche adds. —RHITU CHATTERJEE

Seeing the forest for the methane of the paper. By creating a global model that accounts for varying emission rates on the basis of temperature, light, leaf production, and changing seasons, Butenhoff and Khalil have a template into which they can drop future information about emission rates by different plant species across the globe. jupiterimages

In January 2006, researchers announced that plants exhale methane. Though the amount from each plant is tiny, it adds up globally to a sizable slug of the potent greenhouse gas. Researchers have been scrambling ever since to understand the finding. More than a year later, scientists are closing in on the amount of methane potentially released globally by plants. Yet independent confirmation of the basic discovery and its mechanism remains elusive. If plants do indeed make methane, it is probably not enough to throw the entire methane budget out of whack, according to a new analysis published in this issue of ES&T (pp 4032–4037). The original discovery, published in Nature (2006, 439, 187– 191), estimated that plants spew 62–236 million metric tons per year (t/yr) of methane globally. That would rival major methane sources, such as wetlands, and would mean a major rethinking of the budget. The new ES&T study is so far the “most comprehensive and detailed analysis” of factors expected to affect methane emissions from plants, says study coauthor Aslam Khalil of Portland State University. The study ratchets the plant source down to 20–60 million t/ yr of methane, enough to be “still important” but “on par with the smaller emission sources”, says Chris Butenhoff, a doctoral candidate in Khalil’s lab and lead author

Scientists still don’t know how plants make methane.

But first, scientists will need to learn much more about this enigmatic process. The first report that living plants make methane came from a team led by chemist Frank Keppler in Germany. Most surprising, they concluded that plants make the gas in the presence of oxygen; this runs counter to any known biological mechanism. Only microbes were thought to have methane-making ability, and then only in oxygen-free conditions. The discovery was met immediately with both skepticism and


wild speculation. Because the total amount of methane in the atmosphere is well measured, the methane coming from plants would have to be subtracted out of other known pools to balance the budget. But what to cut, and by how much? Wetlands are the biggest natural source, with a large range (100–200 million t); some scientists thought perhaps they had been overestimated. More controversially, some in the natural-gas industry started to agitate for lowering estimates of human-caused methane sources. A spate of papers followed, reanalyzing global estimates and chipping away at the higher end of the estimated plant source. Soon it became clear that the warming effect of plant methane would slice off at most a few percent from the cooling effect caused by the CO2 plants take up. The new global estimates still scale up from the small number of emission rates that Keppler got from individual plants. And when it comes to independent lab and field studies confirming that plants do indeed make methane and explaining how, the research community is almost eerily silent. As for why no one else has confirmed emissions, both groups cite the painstaking methods needed to measure subatmospheric levels of methane. The new study uses a “more accurate” approach that refines the initial “rough” estimate, Keppler says. He maintains that the new paper “confirms that plants might be an important source of atmo-

plants,” he says, “but then you can leave [the plant source] out if you don’t need it, because it hasn’t been proven.” In any global budget, “there’s always a bit of slush,” Khalil says. For now, the plant source of methane has become a budgeting slush fund, and the account just got a little smaller. —ERIKA ENGELHAUPT

A nano Trojan horse

Wendelin Stark

A growing body of research has and the paper’s corresponding aushown that nanoparticles can thor. “They can defend themselves readily penetrate cells of various quite well, actually.” types. But it may not be the partiStark, who has previously demcles alone that cause trouble inside onstrated nanoparticle uptake by cells. A new study published in human lung fibroblast cells (Envithis issue of ES&T (pp 4158–4163) ron. Sci. Technol. 2005, 39, 9370– suggests that toxicity is greatly in9376), explains that cell memcreased by harmful metals that branes provide a selective barrier hitch a ride with nanoparticles. against ions, preventing the disResearchers at the Swiss Federal solved metal salts from entering. Institute of Technology (ETH) ZuOnce a metal-containing nanoparrich and the Swiss Federal Laboraticle has penetrated a cell, however, tories for Materials Testing exposed metal ions can leach from the partihuman lung epithelial cells to a cle and generate ROS in the cell inrange of metal-containing nanoterior—in what Stark calls a “Trojan particles and measured levels of rehorse” mechanism. active oxygen species (ROS), chemiMark Wiesner, professor of civil cals that can be released by cells or and environmental engineering at generated by foreign materials. An Duke University, finds it notable excess of these reactive molecules can lead to oxidative stress and celOH•,H2O2,HO2• lular damage, and toxiTiO2/SiO2 cologists have identified nanoparticles ROS generation as a likely OH• – mechanism of nanoparticle toxicity. In cells exposed to cobalt oxide and Catalytic surface manganese oxide nanoparticles at 30 parts per 50 µm million, ROS generation was as much as eight times greater than in control cells exposed to an equivalent amount of cobalt or manganese salts. “What we see with the cobalt Cultured human and the manganese is, if we take 50 µm lung cells (A 549) them as their chlorides, the cells When human lung epithelial cells (botdon’t like it, but they’re not dying tom) take up metal-containing nanoparof the stuff either,” says Wendelin ticles (left), harmful molecules can be Stark, head of the Functional Magenerated in reactions at the nanopartiterials Laboratory at ETH Zurich cle surface (top).

News Briefs Rivers at risk

The world’s 10 most endangered rivers are the Salween, La Plata, Danube, Rio Grande, Ganges, Murray-Darling, Indus, Nile, Yangtze, and Mekong, according to a report published in March by the conservation group WWF. World’s Top 10 Rivers at Risk warns that some rivers are so damaged that, without serious restoration efforts, they could be lost. Others are relatively intact but face massive degradation unless conservation action is taken now. The rivers are threatened by dams and infrastructure projects (Salween–Nu, Danube, and La Plata), excessive water extraction for domestic and agricultural use (Rio Grande–Rio Bravo and Ganges), higher temperatures associated with climate change (Indus and Nile–Lake Victoria), invasive species (Murray – Darling), overfishing (Mekong–Lancang), and pollution (Yangtze).

Virtual nano journal

Now you can learn about the potential risks of nanomaterials without plowing through databases. The International Council on Nanotechnology (ICON) has launched a new tool—VJ-NanoEHS, the virtual journal of nanotechnology safety (www. vjnano.org). In 2005, the organization created an Environmental, Health, and Safety (EHS) database of research papers and abstracts on the environmental and health impacts of nanomaterials. Now, ICON along with Rice University’s Center for Biological and Environmental Nanotechnology has converted the database into a reader-friendly monthly journal format. You can browse the portal by author, journal, exposure pathway, risk exposure group, and so on, or subscribe to an RSS feed to receive the latest information. By doing this, ICON hopes to promote responsible development of the fast-expanding nanotech industry.


JUPITErIMAGES

spheric methane . . . [but] as long as we don’t exactly know each source’s strength, it’s difficult to make any predictions for the future.” Meanwhile, scientists seem a bit unsure what to do with the global flux estimates. “People are using, or not using, these measurements from plants as it suits them right now,” Butenhoff says. If a budget doesn’t balance, “you can add

Environmentalt News that measured levels of ROS generation were so much higher in cells exposed to the metal-oxide nanoparticles than in those exposed to the metal salts. But he believes that it would be helpful to have more detailed information about the types of ROS that were generated and their effect on the cells. In addition to studying pure metal oxides, Stark and his colleagues experimented with 20–75nanometer-sized silica nanoparticles containing 0.5 and 1.6 wt % titanium, iron, cobalt, and manganese—a choice of materials influenced by Stark’s background in heterogeneous catalysis, in which transition metals are often used in redox reactions. The researchers were surprised to find that the in vitro behavior of nanoparticles

containing the four different transition metals matched their relative activities in catalytic reactions. Titanium-doped particles caused the least ROS generation, as expected for a photocatalyst in the absence of light. Cobalt- and manganesecontaining particles generated significantly more ROS than those doped with iron. According to Greg Lowry, professor of civil and environmental engineering at Carnegie Mellon University, the researchers made a good case that the specific metals—and not just the presence of particles in the cell—are driving the ROS generation. “It can be difficult separating the effect of the nanoparticle and the attached material,” he says, “but this work clearly shows different effects be-

Fireworks spiraling into the night sky bring cheer and warmth to people watching from below. They also deliver significant levels of perchlorate into nearby water bodies, according to new research published in this issue of ES&T (pp 3966–3971). Scientists have long suspected that fireworks contribute to perchlorate contamination, but few studies have “directly examined” that connection, says study leader Richard Wilkin, an environmental geochemist at the U.S. EPA’s National Risk Management Research Laboratory. This paper takes the research a step further and definitively links fireworks displays to surface-water contamination. But the perchlorate levels don’t last: Wilkin and his team also found that the contaminant’s concentrations fell to background levels after 1–2 months, possibly because of microbial degradation. Perchlorate in the environment is a human-health concern as well as a risk to wildlife. Levels as low as 100 micrograms per liter (μg/L) are known to cause thyroid prob-

JUPITERIMAGES

Perchlorate from fireworks

Potassium perchlorate is a key ingredient of fireworks.

lems in fish. Perchlorate has been shown to come from many different sources. Natural sources include lightning discharges and fertilizers mined from Chilean nitrate deposits, and anthropogenic sources include ammonium perchlorate, a major component of rocket fuel. Because of the dearth of data on the contribution of fireworks to surface-water bodies, Wilkin and his team sampled water from Wintersmith Lake in Oklahoma, before fireworks and for several days after events during July of 2004, 2005,


tween iron, titanium, cobalt, and manganese on particles that are similar in size, shape, and physical properties.” Although Stark’s results add to the growing body of evidence that nanoparticle toxicity may be a concern, he emphasizes that they are still preliminary. He plans to extend his studies to examine the effect of ROS generation on the cells. Nevertheless, Stark believes that assessments of potential nanoparticle toxicity should be conducted early in the development of new technologies. “Another part of my lab is doing application-oriented research,” he explains, “and I don’t want to be part of any application that is going to have to be corrected down the road.” —LIZZ THRALL

2006, and November 2005. Background levels of perchlorate in the lake averaged 0.043 μg/L. Within 14 hours of the fireworks displays, these levels rose 24–1028 times. The authors attribute the wide range in perchlorate concentrations immediately after the fireworks to several factors, including overall quantity of the fireworks used, efficiency with which the perchlorate was oxidized during the burning of the fireworks, and wind direction and velocity. The levels of perchlorate usually peaked at 1 day following the display and then gradually petered out after 20–80 days. Given that the perchlorate disappearance rate was similar to previously observed microbial degradation rates and was temperature-dependent—reaching a minimum at 12.4 °C—the team suspected microbial involvement. They tested this hypothesis with microcosm experiments in the lab. The microbial fauna from the lake successfully degraded the perchlorate, whereas sterilized lake waters showed no change in perchlorate levels. The rate of degradation was dependent on the nitrate concentrations—the microbes preferred to

ters. There are several trace heavy metals that also increase with fireworks that can be considered as tracers, he says. “If perchlorate disappeared but this tracer concentration remained stable, one could follow the argument with greater faith that it just did not disappear by dilution into deeper waters.” Andrew Jackson, an environmental engineer at Texas Tech University, notes that many transient sources, such as bleach, used for water treatment among other things, or certain herbicides “can act as exposure sources.” “Nobody is really addressing what the potential exposure is from all these different sources,” Jackson says. —RHITU CHATTERJEE

Perfume, perfume everywhere

USDA

Synthetic musk fragrances are added to countless consumer items—lotion, shaving cream, shampoo, conditioner, detergent, fabric softener, air freshener, household cleanser, even some “unscented” products—to enhance their appeal. A decade ago, musks were found in human breast milk in Europe, raising a red flag. Now, research published in this issue of ES&T (pp 3815–3820) shows even higher levels of polycyclic musks in breast milk from U.S. mothers. Synthetic musks are present in any consumer product that smells good, notes corresponding author Kurunthachalam Kannan, a toxicologist at the State of New York Department of Health.

No one is sure how fragrance chemicals affect babies.

Because of toxicity concerns, the use of nitro musks, such as musk xylene (1-tert-butyl-3,5-dimethyl2,4,6-trinitrobenzene) and musk ketone (4-tert-butyl-2,6-dimethyl-3,5-dinitroacetophenone) declined in the last two decades. Their replacements, the polycyclic musks—most commonly HHCB (1,3,4,6,7,8-hexahydro-4,6,6,7,8,8hexamethylcyclopenta[g]-2-ben zopyran) and AHTN (7-acetyl1,1,3,4,4,6-hexamethyl-1,2,3,4-tet rahydronaphthalene)—became widespread in beauty, household, and other products. The toxicology of polycyclic musks is not well established, says Kannan. Although effects such as endocrine disruption are seen only at high doses in animals, one report suggests that the chemicals may enhance toxicity of other compounds (Environ. Health Perspect. 2005, 113, 17–24). Musk levels varied widely in the new ES&T study. On a daily basis, infants were estimated to ingest 297 ± 229 nanograms (ng) musk xylene, 780 ± 805 ng musk ketone, 1830 ± 1170 ng HHCB, 656 ± 614 ng AHTN, and 649 ± 598 ng HHCB-

News Briefs EPA’s benefits lie in its rules

Regulations issued by the U.S. EPA account for most of the benefits to society from federal rules, according to a draft report from the Office of Management and Budget (OMB). In its 10th annual Report to Congress on the Costs and Benefits of Federal Regulations, OMB finds that in 2006, seven major rules were issued. These provided $6.3–44.8 billion in annual benefits. The total cost to the economy is estimated at $3.7–4.2 billion. EPA’s rule that tightens the national ambient air quality standard for particulate matter accounted for 60–89% of the benefits and 67–70% of the costs. OMB prepares the president’s budget request and evaluates the effectiveness of agency-level programs. To read the report, go to www.whitehouse.gov/omb/inforeg/ 2007_cb/2007_draft_cb_report.pdf.

A future for coal

Coal-fired power plants will continue to provide energy far into the future without disastrous climate effects, if the U.S. electricity industry and the government move quickly on CO2 capture and sequestration (CCS) technologies, a report from the Massachusetts Institute of Technology finds. The Future of Coal stresses that although CO2 capture is possible and economical, it hasn’t been commercially proven. The authors call for several large-scale, governmentsupported, integrated CCS projects to establish public confidence in the technologies and to prepare for high future demand. A national regulatory regime that spells out protocols for site selection, injection, and operation, and resolves a host of issues, including property rights, liability, and site monitoring, should be undertaken with “far more urgency than is evidenced today,” the academics write.


JUPITERIMAGES

use nitrate for food before attacking the perchlorate. “The real impact of it is in helping to fill data gaps in our understanding of potential sources of perchlorate to the environment,” says environmental toxicologist Todd Anderson of Texas Tech University. The findings also illustrate that “natural systems have the ability to naturally degrade perchlorate over a short time interval,” says Wilkin. However, Purnendu (Sandy) Dasgupta, a perchlorate expert at the University of Texas at Arlington, says that because diffusion is temperature-dependent, disappearance of perchlorate could also be due to gradual diffusion of the contaminant into lake wa-

Environmentalt News lactone—an HHCB oxidation product found in the milk samples—for which no toxicity data exist, says Kannan. HHCB-lactone is present in consumer products, and it is formed during the manufacture of HHCB or by oxidation within the consumer product, according to first author Jessica Reiner, a Ph.D. candidate at the State University of New York at Albany. Staci Simonich, an environmental chemist at Oregon State University, says it’s not surprising that these musks are present in U.S. breast milk. She suspects that the wide variation in concentrations in the milk samples is due to lack of a maternal “clean catch”—possible contamination of milk samples by musks transferred directly from the mothers’ hands or nipples— combined with different patterns of product usage and maternal

uptake. “Even if their hands were washed, it could be with soap that contains fragrances,” she says. The data confirm that musk fragrances can be metabolized and that, ultimately, people can control their exposure. That is good news, says Simonich. Martin Scheringer of the Swiss Federal Institute of Technology Zurich has studied fragrance usage with scenario-based risk assessment, a method designed to analyze consumer habits and their influence on exposure ( J. Ind. Ecol. 2005, 9, 237–258). According to Scheringer, “it is consumer habits and dermal exposure that determine consumer exposure to musk fragrances, at least for adults.” Recently, Aaron Peck of the Skid away Institute of Oceanography and Keri Hornbuckle of the University of Iowa described the en-

vironmental persistence of these fragrances (Environ. Sci. Technol. 2006, 40, 5588; 5629–5635). Peck, who chooses to limit these compounds in his own household, says, “Clearly, babies and infants are exposed to significant quantities of these chemicals. There is a need for studies of the effects of these compounds on small children.” “Our understanding of the effects of this exposure is limited. I hope that we don’t have the regrets for fragrances that we now have for PCBs,” Hornbuckle says. You can reduce your body burden by choosing fragrance-free products. “If it says fragrance-free, it should be fragrance-free. If it says unscented, there may be perfumes in there to mask the malodor of the ingredients,” Simonich says. —BARBARA BOOTH

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