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• Many mass-market hair care products rely on harsh chemicals that can cause follicle, skin and eye irritation. In some cases, ingredients have been implicated in respiratory, immune and endocrine problems, even cancer. Fortunately, there is now a wide range of greener, healthier hair care products available.

Many common hair care products, including shampoos, conditioners and hair sprays, can pose health hazards. Most of the shampoos for sale on supermarket and drugstore shelves use a chemical called sodium laureth sulfate (or one of its derivatives), a foamy de-greaser that can cause follicle, skin and eye irritation, and which has been linked to some cancers when combined with other common shampoo ingredients.

Meanwhile, mass-market conditioners typically rely on so-called quaternary compounds to produce thicker, silkier and tangle-free hair, but these chemicals can also irritate the skin and eyes and likewise have been linked to cancer. As for hair spray and other styling products, most work by coating the hair with polyvinylpyrrolidone (PVP), a plastic polymer that has been dissolved in solvents to keep it flexible. Environment Canada, Canada’s counterpart to the U.S. Environmental Protection Agency, classifies PVP as a medium health priority, although phthalates, triethanolamine, parabens and other hair spray ingredients may be more harmful, having been linked to respiratory, immune and endocrine problems as well as cancer.

Luckily for those who spend a lot of time and money getting their hair to look, smell and feel just right, a wide range of greener, healthier hair care products has emerged in recent years. Aveda has been a pioneer in the industry ever since Horst Rechelbacher launched the company in 1978 after visiting India and witnessing the healing powers of Hindu medicine and aroma. Today the company offers seven hair product lines tailored to different hair types, with the majority of the ingredients derived from plants, non-petroleum minerals or other natural sources. Furthermore, upwards of 89 percent of the essential oils and raw herbal ingredients Aveda uses in its hair cars products are sourced from certified organic producers.

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• Only eight percent of U.S. homes use oil heat today. Natural gas is both cheaper and has lower carbon emissions than oil, though it is still a fossil fuel and its green-friendliness is overstated. Most eco-advocates would rather see a shift to truly renewable heating sources like geothermal or solar.

Dear EarthTalk: Is it true that gas furnaces cost less to run and burn cleaner than their oil counterparts? If I make the switch, how long should I expect it to take for me to pay back my initial investment? And are there any greener options I should consider? — Veronica Austin, Boston, MA

It is true that natural gas has been a more affordable heat source than oil for Americans in recent years. The federal Energy Information Administration (EIA) reports that the average American homeowner will pay only about $732 to heat their home with gas this winter season (October 1 through March 31) versus a whopping $2,535 for oil heat. While the price of natural gas has remained relatively stable in the last few years, oil prices have been high and rising thanks in large part to continued unrest in Middle Eastern oil producing countries. Just two years ago the average winter home oil heating bill was $1,752.

While oil prices are likely to remain high and volatile in the foreseeable future, most energy analysts agree that pricing for natural gas, much of which is still derived domestically, is not expected to rise or fluctuate substantially in the U.S. any time soon. According to EIA economist and forecaster Neil Gamson, the U.S. already has a glut of natural gas and expects even more domestic production to come online soon as drillers are set to open up the Marcellus Shale in Pennsylvania and New York to more gas development.

Only about eight percent of U.S. homes are on oil heat today. Most are in the Northeastern U.S. and were built back in the day when oil was the cheapest way to keep toasty through the long winters. Many utilities have since put gas lines into neighborhoods that didn’t have them in the past, opening the door for homeowners to switch out old inefficient oil furnaces for more efficient gas units.

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• Advocates of thorium to power nuclear plants say that the element is safer than uranium, and that its waste cannot — like the plutonium waste of uranium fission — be re-formulated for nuclear weapons.

Dear EarthTalk: Thorium is a naturally occurring element that is supposedly more available, more efficient and safer to use than uranium for generating nuclear energy. Is this true and, if so, why haven’t we made the switch? — Jane Westermann, Austin, TX

Thorium, a naturally occurring radioactive element found in abundance in the Earth’s crust all around the world, might well be a better fuel source than uranium for nuclear power generation for a variety of reasons. First and foremost, just one ton of the silvery metal can produce as much energy as 200 tons of uranium or 3.5 millions tons of coal, according to Nobel laureate Carlo Rubbia of the European Organization for Nuclear Research (CERN). Another advantage is that it comes out of the ground as a 100 percent pure, usable isotope. Unlike uranium, which contains only 0.7 percent fissionable material, thorium doesn’t require enrichment to be used in nuclear reactors. Also, the spent-fuel waste from thorium fission cannot be re-formulated for nuclear weapons like plutonium, the waste product of uranium-based fission.

Also, proponents say that thorium doesn’t require the high temperatures and mitigation equipment of uranium-based reactors. “The plants would be much smaller and less expensive,” Kirk Sorensen, a former NASA rocket engineer and now chief nuclear technologist at Teledyne Brown Engineering, told the UK’s Telegraph last year. “You wouldn’t need those huge containment domes because there’s no pressurized water in the reactor.” With no high temperatures, thorium reactors can’t “melt down” and release radiation.

“Once you start looking more closely, it blows your mind away,” adds Sorensen. “You can run civilization on thorium for hundreds of thousands of years, and it’s essentially free.” The advocacy-oriented Thorium Energy Alliance reports that there is “enough thorium in the U.S. alone to power the country at its current energy level for over 1,000 years."

Nuclear researchers in the U.S. first contemplated using thorium as a nuclear energy feedstock back in the 1940s, but its lack of feasibility in making nuclear weapons put it on the back burner, where it has sat for the last six decades despite various attempts to revive the technology for practical use. In Russia, China and India, thorium reactors represent the next generation of nuclear power. India possesses about a quarter of the world’s thorium reserves. The country is working to develop a network of large thorium-based reactors, and plans to meet 30 percent of its electricity needs with thorium by 2050.

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• The practice of shark finning to make shark fin soup, a delicacy mostly in Asian cultures, has taken a serious toll on shark populations worldwide. Besides being inhumane to sharks, consumption of shark fin poses a serious threat to human health since they contain an extremely high concentration of mercury and other toxins now omnipresent in our oceans.

Dear EarthTalk: What is shark finning and why have several U.S. states outlawed it? — Betsy Englund, Tampa, FL

Shark finning is the practice of catching sharks, hacking off their fins, and returning them to the ocean (maimed and unable to swim or circulate oxygen through their systems) where they starve to death, suffocate or get eaten by other predators. Fishermen sell the fins, typically on the black market, for use in shark fin soup, a delicacy throughout Asia and increasingly in other areas of the world with large Asian populations. Analysts value the worldwide market for shark fins at upwards of $1.2 billion annually.

“As a result of China’s expanding economy and rising affluence, an increasing number of people can now afford the soup, priced at up to $100 per bowl, and demand has risen dramatically,” reports the non-profit WildAid. “Though shark fin soup represents status in Asian culture, the fin itself adds no flavor, nutritional or medicinal value.” The group adds that the consumption of shark fin poses a serious threat to human health since they contain an extremely high concentration of mercury and other toxins now omnipresent in our oceans.

Besides being inhumane, shark finning is taking a heavy toll on shark populations. According to the non-profit Animal Welfare Institute, upwards of 73 million sharks are killed each year for their fins alone. Another 50 million die annually as “bycatch” when they become entwined in fishing nets targeting other seafood (some fishermen do make use of this bycatch by selling off what fins, cartilage, liver oil and meat they can). As a result of these multiple threats, the International Union for Conservation of Nature (IUCN) estimates that a third of all shark species are nearing extinction, with some species declining by more than 80 percent in recent decades.

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• Only 10 U.S. states have "bottle bills" requiring deposits on some beverage containers so consumers will return them. Those states recycle 70 percent of their bottles and cans, 2.5 times more than states without bottle bills. The beverage industry has spent millions fighting bottle bill legislation, even though beverage containers make up 5.6 percent of the U.S. waste stream.

Dear EarthTalk: Why don’t more states mandate deposits on beverage bottles as incentives for people to return them? Most bottles I’ve seen only list a few states on them. — Alan Wu, Cary, NC

So-called bottle bills, otherwise known as container recycling laws, mandate that certain types of beverage containers require a small deposit (usually five or ten cents) at checkout beyond the price of the beverage itself. Customers can return the empty containers later and reclaim their nickels and dimes. The idea is to provide a financial incentive for consumers to recycle and to force industry to re-use the raw materials.

According to the Container Recycling Institute (CRI), a California-based non-profit which encourages the collection and recycling of packaging materials (and runs the website BottleBill.org), the benefits of bottle bills include: supplying recyclable materials for a high-demand market; conserving energy, natural resources and landfill space; creating new businesses and green jobs; and reducing waste disposal costs and litter. The 10 U.S. states that currently have container recycling laws recycle at least 70 percent of their bottles and cans; this amounts to a recycling rate 2.5 times higher than in states without bottle bills.

Beverage containers make up a whopping 5.6 percent of the overall U.S. waste stream, so every bottle and can that gets recycled counts toward freeing up landfill space. And CRI reports that beverage containers account for some 20 percent of the greenhouse gas emissions resulting from landfilling municipal solid waste and replacing the wasted products with new ones made from virgin feedstock. So by promoting more recycling, bottle bills indirectly reduce our carbon footprints.

The 10 U.S. states with bottle bills are California, Connecticut, Hawaii, Iowa, Maine, Massachusetts, Michigan, New York, Oregon and Vermont. Delaware’s legislature repealed its bottle bill after almost three decades on the books last year as the state’s bottle recycling rate had dropped to just 12 percent due to more and more retailers refusing to deal with the hassle of accepting returned containers. In place of its bottle bill, Delaware enacted a $0.04/bottle recycling fee that will help defray the costs of starting up a curbside recycling pickup system to service the entire state.