Who’s toblame for carbon dioxide emissions to the atmosphere, persistent dioxins, PCBs,vinyl chloride, perchlorates, elevated concentrations of nitrates in streamwater throughout the world, and unusual fish kills? The initial knee-jerkreaction is to lay the blame on present-day humans (read: ourselves), endlesslyaccused of fouling our own nest, and there’s some truth to this. No doubt wehumans are responsible for many egregious environmental actions, but here’ssomething new. Recent research has shown that some of the pollutants heretoforeblamed on industrial activities can now also be laid at the doorstep of MotherNature.
Dioxins from Burning Wood and Biomass
Dioxins,for example, are ubiquitous, toxic, and environmentally persistentorganochlorine compounds, which have been assumed to be by-products of theorganochlorine-based industries that underwent rapid expansion during the 1950s.Yet R. R. Bumb and colleagues found dioxins in soot from wood burning ovens.(1) Thisshows that dioxins were present on Earth from the first fire of forests orgrasslands. Can’t blame man for dioxins in 40 million year-old claydeposits, since he wasn’t around at the time.(2)
PrzemyslawMastalerz notes, “Comparisons of industrial emissions of dioxins withemissions from wood and biomass burning are not possible at present becauseemissions from wood burning are not yet sufficiently quantified, and there is noconsensus on emissions from industrial sources. Published estimates of globalindustrial emissions vary from less than 100kg to 3,000kg annually. In view ofthese numbers, it is probable that wood-burning is the most important source ofdioxins in the environment. There is no doubt that learning the exact balance ofdioxins is very important for our understanding of the contamination ofenvironment. It seems peculiar, therefore, that the environmentalists who spareno effort to measure dioxin emissions from incinerators of hospital waste orhuman corpses show so little interest in wood and biomass burning.”(3) AnEPA study concluded a single trash-burning barrel in a homeowner’s backyard canrelease as much dioxin into the air as a well-controlled municipal wasteincinerator.(4)
In 2002,Pirjo Isosaari and his colleagues found dioxins in sediments that were over8,000 years old in a lake in Finland. An added interesting result of this workwas that besides dioxins, these researchers also found PCBs.(5) This is unusualbecause supposedly PCBs have no natural sources and their formation in thepre-industrial era appears not to be possible. No explanation has been offered.However, natural sources of PCBs may not be as far-fetched as it seems at firstblush.
Researcherswith Canada’s Wildlife Service discovered in marine aquatics an unusualbrominated and chlorinated chemical, C10H6N2Br4Cl2(1,1-dimethyltetrabromodichloro-2,2-bipyrrole), that behaves like PCBs.(6) Theychristened the chemical HDBPs for Halogenated Dimethyl BiPyrroles (7).Characterization and speculation on how it originates cast doubt on the premisethat substances combining chlorine and organic molecules do not result frombiosynthesis (production of a chemical compound by a living organism). Thesechemicals were found in Pacific Ocean and Atlantic Ocean samples but not insamples from the Great Lakes, so industry couldn’t be blamed for their existence.Furthermore, the apparent absence of HDBPs from the five freshwater Great Lakesalso suggests that they are not airborne.(8)
Recently, Andrew Meharg and Kenneth Killhamreported in Nature that the burning of coastal peat was a significant source ofdioxins long before the industrial revolution.(9) The burning of peat, which isdecaying tropical plant matter, was how people in much of the British Isles keptthemselves warm during the eighteenth and nineteenth centuries, and theresearchers report that Scotland, with well under half a million people,probably produced as much as a tenth of the amount produced by municipal wasteincinerators in the entire United Kingdom today. The Scotland Isle of Hirta,which was evacuated in 1930, still has dioxin in the soil from peat burning,clear evidence that modern humans were not the first to generate large amountsof dioxins.(9)
Peat burning can also spew massive amounts ofcarbon into the atmosphere. Emissions from the 1997-1998 wildfires in Indonesiaconsumed vast amounts of peat and released a total of 0.81 to 2.57 billion tonsof carbon into the air. This amounts to 13 to 40 percent of the average annualamount produced globally from combustion of fossil fuels. Susan Page and hercolleagues report that the Indonesia fires contributed greatly to the largestannual increase in atmospheric carbon dioxide concentration detected sincerecords began in 1957.(10) The emissions from the Indonesia fires werecomparable to the global carbon uptake by the terrestrial biosphere in a typicalyear, yet they came from a relatively tiny area of the globe.(11) These datasupport the case that some events can significantly affect atmospheric carbonworldwide and throw a monkey wrench into most global temperature modelingstrategies.
NatureMaketh and Taketh Away Ozone
Jay Lehrasks the question, what do you get when you go into the North Woods, a great,beautiful unspoiled area where there is no industry for miles? The answer is youinhale the pine odor. Guess what? Pine odor is made up of polycyclic aromatics,carcinogens, in the cleanest air we supposedly have in this country.(12) Further,in regards to forests, when discussing neglected sources of ozone, Janet Pelleysays, “Scientists are beginning to blame local forests and pollutants blownin from overseas for the fact that concentrations of ground level ozone and itsaccompanying smog have not declined during the past ten years in the UnitedStates, despite cuts in ozone precursors. Thus, national smog fightingregulations may actually be doing a better job than they have been given creditfor, but measurably reducing ozone levels may require international efforts andrethinking forestry management.”(13) Research by Allen H. Goldstein, anatmospheric chemist at the University of California, Berkeley, suggests that theamounts of ozone absorbed by trees in a California pine forest also suggest thepresence of unidentified volatile organic compounds (VOCs). He proposes thatthey’re related to terpenes.”(14)
PerettiHari and his colleagues report that global NOx emissions from boreal coniferousforests may be comparable to those produced by worldwide industrial and trafficsources. Hari suspects that other evergreens and perhaps even all plants mightalso release the compounds under many natural conditions.(15) Jessica Germanadds that tree emissions can react with humanmade compounds to make chemicalsthat further pollute the air or contribute to climate change. She quotes AlexGuenther of the National Center for Atmospheric Research in Boulder, Colorado,regarding large poplar plantations in Oregon that “actually are changingthe chemistry of that region because they have much higher emissions rates oforganic gases than many other trees do.”(16)
Volatilehalogenated organic compounds (VHOC) contribute to stratospheric ozone depletion.It’s becoming more evident that halogenated compounds of natural origin cancontribute significantly to the levels of VHOC in the atmosphere. The oceans area major source, and some terrestrial sources include wood rotting fungi, biomassburning, and volcanic emissions — in addition to human activity. Arecently identified terrestrial source of naturally occurring VHOC is in soilsand sediments, where halide ions can be alkylated during the oxidation oforganic matter by an electron acceptor source, as Dr. Frank Keppler and hiscolleagues report: “Sunlight or microbial mediation are not required forthese reactions and such abiotic processes could make a significant contributionto important atmospheric compounds CH3Cl, CH3Br, and CH3I.”(17)
VinylChloride from the Earth, Nitrates from the Sea
Vinylchloride, a highly reactive and toxic substance that is widely used in industry,was thought to be exclusively manmade, or the degradation product of otheranthropogenic substances, such as trichloroethylene and tetrachloroethylene. Notany longer. Frank Keppler and his colleagues have demonstrated that vinylchloride also comes from natural sources such as soil. They conclude, “Thepresumption that vinyl chloride is solely manmade must now be considered asincorrect. There is no doubt that industrial and anthropogenic activity hascontributed significantly to the burden of vinyl chloride in the environment,but our results show that vinyl chloride in the environment also has naturalsources. One possible source comes from the reaction of organic matter, Fe(III),and chloride. As humic substances, catechols, Fe(III), and chloride ions arewidespread in nature, the magnitude of this soil source of VC and other volatilechlorinated substances is potentially enormous and could make a contribution tothe budget of vinyl chloride in the environment.”(18)
Elevatedconcentrations of nitrates in stream water throughout the world have been blamedon human activities. Again, recent research lays some of the blame on MotherNature, which until now had been considered innocent. Seawater has been shown tobe a possible significant source of some nitrates in one study,(19) and anotherrevealed that bedrock contains fixed nitrogen that contributes appreciableconcentrations of nitrate to surface waters in certain California watersheds.(20)Adele Chuck and her colleagues report, “Measurements of methyl and ethylnitrate in seawater and air samples along two Atlantic Ocean transects providethe first direct evidence for an oceanic source of these compounds. Equatorialsurface waters were highly supersaturated (up to 800%) in both species, with thewaters in the temperate regions generally being closer to equilibrium.” Themechanism behind all this is unclear at present, but the findings raisequestions about the formation of nitrogen compounds in remote marineenvironments and could have important implications for the formation anddestruction of tropospheric ozone.
There’smore to the story. Another study has revealed that bedrock containing highconcentrations of fixed nitrogen contribute appreciable concentrations ofnitrate to surface waters in certain California watersheds, to the extent thateven small areas of these rocks have a profound influence on water quality.”As 75% of the rocks now exposed at the Earth’s surface are sedimentary inorigin, and as these rocks contain about 20% of the global nitrogen inventory, ‘geological’nitrogen may be a large and hitherto unappreciated source of nitrate to surfacewaters.”(20) The same geological formations where the nitrogen was found”extend for 300 km along the western flank of the Sierra Nevada, indicatingthe potential for nitrate contamination of much of California’s surface watersupply.” As with nitrates in the ocean, here’s another case where nitrogenas a non-point source of contamination needs to be reevaluated.
It’sRaining Rocket Fuel; Thar She Flame-Retards
Controversyhas swirled around estimates of the health risks posed by perchlorate indrinking water. The source of most contamination has been facilities thatmanufacture or use perchlorate-containing rocket fuel. However, recent workshows that traces of perchlorate can be found in rain and snow and can becreated in lab experiments simulating tropospheric processes. This suggests thatthere is a natural flux of atmospheric perchlorate to the earth and a naturalperchlorate level. Once again, nature mimics industry.(21)
Brominatedorganic chemicals are used as flame-retardants for electronics, furniture, andtextiles. They have been found throughout the environment, accumulating in fishand marine animals and sometimes detected in human breast milk. Some researcherssuspect that these compounds may affect animal and human health, and severalcompounds have been banned.(22) Recent work at Woods Hole OceanographicInstitution (WHOI) debunks some of this. Researchers at WHOI have found that twochemicals accumulating in the tissues of marine animals and suspected to bemanmade pollutants actually came from natural sources.(23)
Thechemicals, methoxylated polybrominated diphenyl ethers or MeO-BDEs, found inwhale blubber, raise questions about the accumulation of both natural andindustrial compounds in marine life and is causing researchers to rethink thesources and fates of many chemical compounds in the environment. Michal Raucherreports, “This discovery is significant because environmental activistshave been sending scary messages about the dangers of all the chemicals in ourclothing, furniture, and pesticides from human-produced sources. Theirintimidating statements urge us to stop using certain chemicals because theyaccumulate in humans, animals, and the food we eat and air we breathe — butscientists are discovering that the chemicals found in wildlife are of naturalorigin.”(24)
How werethe chemicals found? The researchers used a mass spectrometry facility at WoodsHole that does precision carbon dating. They took advantage of the fact thatnatural sources have a detectable radiocarbon signal while human producedsources from petrochemicals do not.(23) This is another example of advances inanalytical techniques that are helping find chemicals previously impossible toanalyze. Says Gordon Gribble of Dartmouth College, “This radiationtechnique is very exciting. There’s been no other way to distinguish the originof the same compounds that are produced by both nature and man.”(22)
Note thedates on the references discussed in this article. These are all very recentfindings. Remember this next time you hear about how we humans are addingpollutants to the atmosphere. Mother Nature is providing a lot of help, and astime goes on we’re finding she’s not an innocent bystander watching us createhavoc with our environment.
For decades, environmental groups have said thatnature would never make brominated compounds or other halogenated chemicals. Butin recent years these compounds have been found in forest fires, volcanic ash,soil, peat bogs, and myriad marine organisms.This is one examples of nature mimicking industry, and there are many more.Vinyl chloride, dioxins, volatile halogenated organic compounds, andperchlorates are formed in nature, and nitrates from sea water and bedrock havenow been shown to be significant sources adding to the
increasingamounts of nitrates observed. These recent results influence regulatory work,making it impossible to assign elevated concentrations purely to industrialsources. Instead of setting demands on manmade contributions to the environmentwith the goal of eliminating or minimizing various chemicals, it would benecessary to distinguish natural background from anthropogenic pollution. Andwith the passage of time and with improved analytical techniques this is amoving target.
1. R. R.Bumb, et al., “Trace Chemistries of Fire: A Source of ChlorinatedDioxins,” Science, 210, 385 (October 24, 1980)
2.Joseph B. Ferrario, Christian J. Byrne and David H. Cleverly,”2,3,7,8-Dibenzo-p-dioxins in Mined Clay Products from the United States:Evidence for Possible Natural Origin,” Environmental Science &Technology, 34, 4524 (2000)
3.Przemyslaw Mastalerz, The True Story of DOT, PCB, and Dioxin, (Wroclaw, Poland,Wydawnictwo Chemiczne, 2005), 67
5. PirjoIsosaari, Hannu Pajunen and Terttu Vartiainen, “PCDD/F and PCB history indated sediments of a rural lake,” Chemosphere, 47, 575 (2002)
6.Sheryl A. Tittlemier, et al., “Identification of a Novel C10H6N2Br4Cl2Heterocyclic Compound in Seabird Eggs, A Bioaccumulating Marine Natural Product?,Environmental Science & Technology, 33, 26 (1999)
7. R. J.Norstrom, private communication, August 2, 2000
8. TomSpears, “The Mystery of ‘SNOB’ — Nature’s PCB?”, Priorities forHealth 12, No 2, 10 (2000)
9.Andrew A. Meharg and Kenneth Killham, “A pre-industrial source of dioxinsand furans,” Nature 421, 909 (February 2003)
10.Susan E. Page, et al., “The amount of carbon released from peat and forestfires in Indonesia during 1997,” Nature, 420, 61 (November 7, 2002)
11.David Schimel and David Baker, “The wildfire factor,” Nature, 420, 29(November 7, 2002)
12. JayH. Lehr, “Toxicological Risk Assessment Distortions,” in RationalReadings on Environmental Concerns, Jay H. Lehr, Editor, (New York, Van NostrandReinhold, 1992), 682