Saturday, March 31, 2018
Book Review: Living Downstream: An Ecologist’s Personal Investigation of Cancer and the Environment – by Sandra Steingraber, Ph.D. (Da Capo Press 1997, 2nd Ed. 2010)
This is an interesting account of the possible relationships between chemicals, particularly synthetic organic chemicals, and incidence of cancer. By nature, it is difficult to discern prime causes of cancer and what might just be influences. The environment a body encounters and imbibes is certainly a factor. She does a good job of stating evidence and trying to tease out relationships in light of both her scientific prowess and her very personal long and thus far successful battle with bladder cancer, diagnosed when she was 20. It is also good as a personal account of the anxieties, hopes and fears, of having cancer, quite touching at times. She is a veteran of over 70 cytoscopic exams where tubes were inserted into her bladder.
In the intro to the 2nd edition she notes that it has been thirty years since she was first diagnosed. When she was diagnosed she was asked by her urologist if she ever worked in a tire factory, the aluminum industry, or with textile dyes. She was asked because bladder cancer is the cancer most thought to be due to exposure to hazardous chemicals. Of all the chemicals used in our society very few have been specifically tested for carcinogenicity – about 2%, although that increases if we extrapolate and categorize by type. Many chemicals known to cause cancer in animals are used in food and consumer products. Genetic factors are extremely important in susceptibility to cancer so that it makes sense that the genetically susceptible are very sensitive to exposure to carcinogens in the environment.
Steingraber’s information sources include the Harvard Medical School library where she did post-doctoral research, right-to-know laws, cancer registries, published studies, and reports about levels of environmental contaminants like pesticides and other chemicals and air pollution. She notes the 1986 federal right-to-know law which requires industrial interests to keep databases of the release of initially some 650 toxic substances into the environment. The database became the Toxics Release Inventory (TRI). This allowed researchers to compare where those releases occurred with local cancer rates and patterns. From 2001 to 2008 the TRI was scaled back and thousands of facilities were no longer required to report.
Steingraber does acknowledge that cancer causation is complex and a recent analysis from Johns Hopkins University notes that most cancers to not have a discernable cause. She notes cancer causation used to be divided among three variables: genes, lifestyle, and environment. Newer analyses indicate that those variables often intermingle in complex ways. Genetic factors may involve epigenetic factors – genetic predisposition to cancer is too simplistic. Substances, natural and synthetic may alter gene expression and change gene behavior. She also mentions endocrine disruption, whereby certain chemicals disrupt our endocrine system which affects hormone production, metabolism, and reproduction. Basically, chemicals can interfere with and mimic hormones. She notes the old toxicology adage – “the dose makes the poison,” but also adds that in endocrine disruption the timing is often very important, particularly exposure early in life. Another complicating factor is chemical mixtures and how they interact with one another and with the body as a whole. Steingraber is an advocate of the Precautionary Principle, which is favored in Europe but has always been a hard sell in the U.S. I don’t agree with her on this – sometimes being overly cautious can cause more harm than good and I think each individual case should be evaluated separately rather than fall under a single regulatory principle. She favors ‘green chemistry’ but there is as of yet much to work out with it. She notes that petroleum and coal are often the sources of carcinogenic synthetic substances and so favors green energy. Of course, petroleum is also the source of many synthetic chemicals that improve health and make our lives safer and more convenient. The bigger part of toxic chemical releases come from coal-burning power plants and emissions from vehicles. She notes that the death rate from cancer has actually fallen and this is due primarily to the success of smoking cessation programs. However, childhood cancer has slowly but steadily increased over the years. She notes that certain industrial chemicals have been proven to cause cancer among those who work with them so that precautions are needed, including outright banning in some cases.
Steingraber recounts her childhood in Central Illinois prairieland/farmland where part of her family farmed. Illinois is 87% farmland. It has been farmed for a long time and pesticide use is abundant, including the use of atrazine. Atrazine in the environment is high during spring planting and lower in winter. It and its byproducts are found in surface water, air, and groundwater as well. A 1992 study found that one quarter of private wells in Central Illinois contained agricultural chemicals, typically in trace amounts. How they get into groundwater and how much varies according to how much used, how much runs off, and the local geology and groundwater configurations are important factors. Even long-banned DDT and PCBs are still found in the environment due to their chemical stability. She notes that:
“Atrazine remains the most frequently detected pesticide [as of publication 2010] in water throughout the United States, found in three of every four American streams and rivers and 40% of all groundwater samples.”
She gives some info/data and anecdotes about DDT, PCBs, and atrazine and introduces Rachel Carson, who succumbed to cancer and whose work led to DDT being banned. Through the book it can be seen that Steingraber venerates Carson and follows in her footsteps. She recounts her visits to the library at Yale University that houses Carson’s papers. She reproduces some of Carson’s notes about her own cancer and impending death and through narrative stories about Steingraber’s friend Jeannie who had an aggressive form of cancer in her thirties and died from it. Carson’s famous 1962 book, Silent Spring, led to the banning or restricted use of several dangerous pesticides, although the chemical industry fought her. In a few isolated cases these pesticides can be useful according to many – such as in very specific applications to prevent malaria which kills many children around the world in tropical countries with abundant mosquitos. Many say DDT could prevent those deaths but there is no access since it is banned internationally. DDT, PCBs, and possibly atrazine (which is not banned in the U.S. but is in Europe) are in some ways associated with cancer although data and conclusions have been inconsistent. Thus, even with these powerful poisons it is difficult to get incontrovertible conclusions. This makes the much less powerful pesticides in use today like glyphosate much more benign by comparison. Steingraber also recounts Carson’s public appearances to fight the chemical/pesticide industry after Silent Spring was published and her struggling cancer patient appearance as she defended her work. Carson argued that pesticides and other chemicals caused cancer before it was generally ceded that that was the case. Steingraber notes Carson’s ode to citizen activists as helping her to speak out and sees herself in the same light – as an activist as well as a scientist – Steingraber has been vocal in recent years in opposition to oil and gas industry activity near Ithaca, NY where she lives – although I think her focus may be misplaced since the fracking revolution likely produces far more benefit than harm and the fears about water contamination are overblown.
She recounts the experience of having cancer throughout the book, the boredom, the anxiety, the fear, the frustration. She also notes cancer trends and trying to tease out trends from the data that is available. She pours through state and federal cancer registries and compares them to TRI data. She looks at cancer incidence rates = number of new cancer cases per 100,000 people per year. Tracking changes in cancer incidence can lead to discoveries that point to sources. Unfortunately, there are often multiple possible sources so that the availability of many of them may correlate with cancer incidence and yet not be related by cause. The adage “correlation does not equal causation” is often relevant to these statistical epidemiological approaches. Teasing out clear relationships from the data can be difficult. She acknowledges these problems.
Incidence rates can change when new detection technologies appear such as mammography for breast cancer. She explores the trends in breast cancer, noting that breast cancer has been dropping irregularly since it peaked in the 1990’s. There are several possible reasons: decline in women taking hormone-replacement drugs, decline in women getting mammograms, disproportional under-reporting, and declining exposure to causative agents. She notes that breast cancer kills 41,000 women in the U.S. yearly. Another reason cancer trends are hard to track is that it is a slow disease and people move to different localities making cancer by region difficult to calculate evenly. She notes that the overall cancer incidence rate is 463 per 100,000. This is more than twice the cancer mortality rate so more people are surviving cancer. Over 11 million people in the U.S. have cancer, are in remission, or are cured. The cancers that are rising are leukemia, non-Hodgkin lymphoma, soft tissue cancers, kidney cancer, and brain and nervous system tumors. Childhood cancers are rising as well, which suggests environmental factors. She notes that children do receive a higher proportion of any poisons in air and water due to body weight and they don’t have lifestyle factors as adults do. She notes that cigarette smoking causes 85-90% of lung cancer with a very high fatality rate and is thus the largest preventable form of cancer.
Steingraber lauds calls to fund more cancer incidence research as well as research of more potential chemical carcinogens. She notes cancer studies that have grouped people by birth year, by racial/ethnic background, gender, or all of the above. She focuses in on the data about non-Hodgkin lymphomas and notes that people of certain occupations tend to get it such as farm workers and dry cleaning workers. Solvents, PCBs, and certain pesticides (phenoxy herbicides) are suspected sources or triggers. She studies cancer distributions across space and time. One might find cancer clusters and compare them to nearby potential sources of toxins, although one would have to prove that those toxins are there and know something about their toxicological effects. She notes throughout the book that cancer study results are often unclear and inconclusive and can only suggest where and what to study further. She thinks there is a general correlation between industrialization and rising cancer rates. She suggests that increased coal-burning in China and living near a Soviet petrochemical complex in Ajerbaijan correlate well to increasing cancer rates in those places. She implicates coal and petroleum in particular – many synthetic chemicals derive from petroleum. However, it is hard to know how much cancer or cancer influence is derived from petroleum chemicals. We also know that the UV light from the sun causes cancer in those susceptible and that plant substances can be carcinogenic. Lifestyle factors may also stack the deck for or against cancers. Household chemicals, cosmetics, cleaning chemicals, paints, and solvents may be factors. It is hard to know how much with each of these without large, long-lasting, and well-planned studies. More people die of heart disease than cancer (especially now as more and more cancers become treatable) and lifestyle is also a large factor in heart disease. Toxin exposure could be a contributing factor as well. She notes that increasing cancer rates among migrants to a new place certainly suggests an environmental influence.
She calls for a nationwide cancer registry. The National Cancer Institute keeps an atlas of cancer mortality but not incidence (cancer mortality has dropped due to better treatment and sooner detection). She notes a good correlation between cancer mortality and industrial areas. However, she also notes that quality of treatment is a factor and that cancer diagnoses do not seem to correlate as well to industrial activity. She does say that cancer rates seem to match industry more than any other health problems match it. She mentions a study in the UK that correlated leukemia very well to industrial facilities, particularly to those involving chemical solvents at high temperatures. Cancer rates among certain occupations have long been studied: farmers, chemists, dental workers, barbers, hairdressers, firefighters, painters, welders, asbestos workers, miners, printers, fabric and dye workers, certain electronics workers, and plastics manufacturers. Being somehow exposed to dumped chemicals and wastes is also considered, particularly the many Superfund sites. She does also consider methodology and the difficulty of getting from correlation to causation. Here she mentions ecological fallacy as a term meaning to falsely attribute causation to correlation. She complains that uncertainty has been used to delay corrective action for reducing environmental pollution. That can work both ways as those who favor strong regulation of potential toxins often use uncertainty to argue their position – the basis of the Precautionary Principle. It is basically a ‘prove it safe’ vs. a ‘prove it harmful’ debate. I would argue that since many of the toxins are or derive from substances that do much good in the world, including making people healthier and enabling many things – that the burden should be on those to ‘prove it harmful’ for most things – that usefulness to society, cost, and disruption also need to be taken into account.
She goes through a type of epidemiology known as “ecological studies,” which attempt to discern disease trends in large groups. One might study populations where exposure to toxins is likely vs. populations where it is unlikely. Investigation of cancer clusters can be tricky or legitimate requests for such studies can be dismissed by health workers. We are all exposed to various levels of ‘probable carcinogens’ such as metal degreaser trichlorethylene (TCE) as it is in most water supplies. In such cases it is difficult to find a comparison population with no exposure to the toxin. Cancer is more difficult to study because it may take a long time after exposure (to certain toxins) for cancer to develop. People move between exposure and onset. Also, cancer may have numerous causes so that pinpointing it to one cause is not easy. She notes that GIS (geographic information systems) can be very helpful. Environmental epidemiology is wrought with difficulties as well as being amenable to inconclusive results that may suggest causation that is not causation and vice versa.
Steingraber focuses on synthetic organic chemicals as potential sources of cancer although she does not mention that there are natural sources of cancer as well and that some of the synthesized chemicals also do occur in nature, although often in different forms. Crude oil is a natural substance that is toxic if ingested. She notes that:
“Synthetic organic molecules are chemically similar enough to substances naturally found in the bodies of living organisms that, as a group, they tend to be biologically active.”
This is problematic she says. Many organic chemicals are inert in their final forms but active in their intermediate forms during manufacture. If enough of some chemicals get in our systems they may mimic natural body chemicals as is thought to be the way endocrine disruptors act. She also mentions chloroform, considered a probable carcinogen. It is used in many chemical processes and appears in wastewater. It also appears as a byproduct of chlorinated water so removing it may be impossible. Later in the book she does mention favoring alternatives to chlorine use but water companies still prefer chlorine based on cost and feasibility. She laments the ineffectiveness of the 1976 Toxic Substances Control Act (TSCA) which does not require testing for the vast majority of new chemicals on the market. Of course, massive new studies on every new chemical would mean massive animal testing and such tests often involve giving animals massive lethal doses. She notes that barely a handful of chemicals have ever been taken off the market and none for the last nineteen years. Pesticides are regulated differently – Federal Food, Drug, and Cosmetic Act (FFDCA) and Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). In 1986 the Emergency Planning and Community Right-to-Know Act (EPCRA) passed Congress over massive opposition by industry. It spurred the Toxics Release Inventory (TRI) which requires companies to report the total amount of about 650 toxic chemicals released as waste, by-products, and spills every year. TRI was scaled back in 2008 and 2009 citing homeland security concerns since knowledge of where toxins were stored could be used by those wishing to unleash them for terroristic reasons. However, in order to explore whether environmental toxins are influencing cancer incidence one would need to know what is actual in the environment from day to day or at least on avg.
Toxics and pollutants may be concentrated at places like landfills, particularly at those that accept toxic waste such as heavy metals that have been implicated as carcinogens. Steingraber does her own investigative analysis of industrial toxics released into her childhood area of Tazewell County, Illinois.
She goes back again to endocrine disruptors, mainly those that mimic the hormone estrogen. While this is true of several industrial chemicals just today I read an article about naturally-occurring chemicals in the essential oils used in many soaps, shampoos, and lotions also doing the same thing. The substances in the oils are also known to bioaccumulate rather than fully metabolize. Apparently, there are several ways substances (both synthetic and natural) interfere with hormones. Phthalates used in PVC plastic and added to perfumes and lotions are known disruptors as are a rather toxic chemical group known as organochlorines which includes PCBs, TCE, DDT, dioxin, and several others. Organochlorines tend to persist in the environment. Burning plastic produces dioxin and other organochlorines. She mentions the UN Stockholm Convention on Persistent Organic Pollutants (POPs) as inspiring since it seeks to eliminate the use of the most toxic POPs. Several of the worst organochlorines are on the list.
Steingraber favors so-called green chemistry over petroleum chemistry but it is quite difficult to compete with petroleum (or natural gas liquids and derivatives) as feedstocks. She mentions as one green chemistry success story – the development of a soy-based adhesive that replaces formaldehyde in plywood. She argues that green chemistry should be mandated like smoking cessation and exercise – as health-promoting. However, she doesn’t acknowledge that some of nature’s own chemicals, when concentrated and exposed to creatures can cause health problems too. I think she overly focuses on the synthetics. Too many wood ashes concentrated in one spot can contain carcinogenic heavy metals. Wood smoke is highly toxic. An USDA-organic approved fungicide like copper sulfate can be more toxic than commonly used pesticides as can other highly concentrated natural substances. She does acknowledge that pre-synthetic substances like celluloid and castor oil are also environmentally harmful and so does not advocate for banning all synthetic chemicals, only the most harmful ones. While that may seem reasonable some are difficult to replace. However, her activism to ban fracking and an underground propane storage facility suggest that she does advocate bans.
She goes through some case studies of possible relationships between certain pesticides and breast cancer. She also explains why assays – evaluations of biological or chemical substances – can be expensive, messy, and complex. In assays for potential carcinogens animal studies need to involve large amounts of animals who need to be evaluated for years as cancer often takes a long time to appear. For complete understanding such long complex assays would be needed for each potential chemical carcinogen, ideally. Some researchers have advocated for new chemical screening tools since the time constraints and inconclusiveness of animal assays keep a huge backlog of chemicals for which toxicity is unknown. Better knowledge of the interactions of networks of genes, proteins, and receptors has shown that certain chemicals and classes of chemicals disrupt the pathways of these cell functions.
She discovers that her own cancer, a type of bladder cancer called transitional cell carcinoma, also occurs among beluga whales from the St. Lawrence estuary in Canada. Many workers from a nearby aluminum smelting operation also got that particular type of cancer. PCBs, DDT, chlordane, and other toxins are found in the waters and sediment of the estuary. There is also benzo-[a]-pyrene, product of combustion classed as a polycyclic aromatic hydrocarbon (PAH). Liver cancer in fish has also been linked to toxics.
She laments the change from large numbers of small family farms to less farms but bigger more industrialized ones. Using pesticides reduced the need for crop rotation. She recounts her childhood farm experiences in Illinois. While Illinois corn and soybeans are sold for export, most goes to feed livestock. A significant amount also becomes snacks and corn sugar. She also advocates taxing foods of lower nutritional value, like soda to deal with the obesity epidemic. Obesity and weight gain are risk factors for cancer, probably related to hormones and inflammation. She sees the farm belt as overproducing the two – corn and soy – but they make the best animal feed, snacks, and best grain nutrition for export. Also, larger more industrialized farms are way more efficient and reduce overall land use quite significantly. Corn and soy also account for the largest share of herbicide use. Of course , there is also organic, which uses organically approved pesticides, not synthetic, but which may also have some ill effects. Weeds used to be removed by plowing, hoeing, and disking but these were time and labor intensive. They also released more carbon from soils. Modern no-till methods are better for soil health and retain more carbon. Herbicide-resistant varieties developed through genetic engineering. Though she laments that by 2004 a third of Illinois corn was GMO (probably much more now), this is now widely seen as a good thing since overall pesticide use is down. She does not mention this. She invokes herbicide-resistant weeds which can be problematic but have yet to be a huge problem, especially as herbicides are more targeted in place and time to reduce runoff. She laments the continued use of atrazine, banned in the EU, because of its water solubility and ability to spread all over the environment. She also laments the dead zones caused by nitrogen and phosphorus fertilizer runoff overload. She notes that manure is way less used than it used to be (although she doesn’t mention that manure runoff also contributes significantly to the runoff that creates dead zones). Synthetic nitrogen fertilizers are made from natural gas in fertilizer plants. Although she sees that as a problem it is really the basis for improved yields and preventing more global hunger as well as allowing farmers to make a profit and food to be plentiful and cheap. Fertilizer can also be targeted in place and time to reduce runoff, which also can save farmers money. She goes on to advocate organic farming and agroecology. These are of course good things but in terms of yields and reducing land use for agriculture they are still way behind modern mechanized agriculture utilizing synthetic fertilizer. She seems to think organic farming reduced carbon footprints but more recent analysis suggests it’s the other way around, mainly due to less land required for comparable yields = less deforestation/more reforestation. More modern scientific analysis suggests that organic “methods” combined with efficient and smart use of synthetic fertilizers, and genetic engineering will be the best overall solution. More recently there is CRISPR gene-editing that may make GMOs more versatile. Her call to go back to the old ways of farming on a large scale seems rather anachronistic and naive in light of the massive success of modern methods.
Next, she considers airborne toxins that follow the weather to distribute themselves across the globe, even in remote parts of the world such as the Arctic. She mentions that in 2007 one-third of toxins released into the environment were released into the air. However, much of it probably ends up not heavily concentrated. There are chemical reactions that can combine to make new air contaminants from combusted material like how nitrous oxides and volatile organic compounds (VOCs) contribute to photochemical smog/ground-level ozone. This is a well-known pollutant in many urban areas and is considered to shorten life if one lives in an area of chronic smog. She thinks the increase of lung cancer among non-smokers may be attributed to particulates and smog. Oncologists and pathologists have also suggested that air pollutants like nitrogen dioxide may also help cancer spread from other areas to the lungs where it is difficult to treat.
Next, she considers water pollution, noting that it may be responsible for habitat destruction for many riverine species including water fowl. As in many place, she notes that water quality improved in the Illinois rivers due to the requirements of the 1972 Clean Air Act. The 1974 Safe Drinking Water Act set limits of certain chemicals allowable in drinking water. She notes the concept of “enforceable limits” of a few parts per billion of some substances like benzene and TCE where any amount is considered dangerous but water can only be “cleaned” to those enforceable limits. Most limits are in single-digit parts per billion. She notes that as of 2009 there were only enforceable limits established for 90 contaminants. Any device that heats water (showers, dishwashers, washers) can also release VOCs from the water so that water can also contribute to airborne toxics. Some studies have suggested that showers can be more toxic than drinking toxins in water. Again she considers chlorinated water, noting that chlorine combines with contaminants in water to make toxic by-products, some of which are organo-chlorines. She notes that about 600 of those by-products have been discovered with few tested for carcinogenicity. A few are monitored and regulated – trihalomethanes and haloacetic acids – and chloroform being the most common. She favors alternative water disinfection strategies although chlorine has proven to be quite effective and removing chlorine has proved deadly in a few cases. She favors activated charcoal and ozonation but it is unclear how they compare to chlorine in effectiveness and cost. Manure from farms (which she laments the loss of) is the most widely implicated source of water contamination – so protection of source water can be key to preventing contamination. She does mention that using activated charcoal, then aeration, then using chlorine as the final (rather than the first) stage can reduce trihalomethanes – although aeration can make them airborne. She also considers groundwater contamination through time and in different parts of aquifers (groundwater moves slow in some aquifers, faster in others). She notes that contamination in groundwater recharge areas, typically upland is more problematic than in discharge areas, typically lowland. Thus, protection of recharge areas is emphasized. Contaminated groundwater is difficult to remedy.
Next, she considers the effects of garbage incinerators, mainly on airborne contamination. These waste-to-energy plants vary in effect based on how the waste-stream is sorted and how effective are the pollution control systems. In modern times some systems claim 99% of contaminants are removed (although the 1% remaining still worries nearby residents). Places like Sweden use their WTE plants as a source of pride in the use of renewable energy while places in the U.S. may consider them sources of industrial toxicity. Perhaps it depends on how they are marketed and the propaganda. There is a long-standing debate about whether landfilling or WTE plants are better for the environment. Her analysis here is a few decades old so I won’t dwell on it. The bottom line today is how much pollution-control is implemented or in the case of landfills how sophisticated are the leachate collection systems, the groundwater monitoring wells, and the methane collection and pumping systems. Each project should be evaluated separately. Dioxin is one major toxin produced and clearly those who live nearest are the most affected. She documents studies on dioxin and how it may work to lead to cancer but the jury is still out on its effects and what an acceptable level should be. Burning most things produces some dioxins, including burning wood. She favors recycling but that too has costs and it is difficult for recyclers to make money and to get people to do it on a large scale. Zero waste is a nice concept but in reality it is far from achievable without massive changes in social habits.
Next, she considers ‘body burden,’ the sum total of all the effects of ingesting, inhaling, and absorption through skin of contaminants to get an idea of ‘cumulative exposure.’ We can measure the amounts of different contaminants in different parts of the body. The highest amounts of DDT, PCBs, and chlordane were found when those chemicals were most in production and use. Measuring levels of pollutants in people is known as “biomonitoring.” When lead was phased out of gasoline, blood levels of lead in children began to decrease and they ended up decreasing more than the models predicted so we know that changing the levels of some chemicals in the environment can lead to less of them in our bodies in a reasonable amount of time. Biomonitoring has also shown that banning smoking in public places has resulted in less “smoke” in our bodies. In 1999, the CDC began monitoring a group of 5000 people in 15 geographic locations for up to 148 chemicals. One surprise was the amount of flame-retardants we have in our bodies – these are potentially dangerous endocrine-disrupting POPs that we have way more in our bodies than Europeans. She notes that advances in chemistry have made biomonitoring more effective and cheaper. California was the first state to embrace biomonitoring but most states have followed suit.
She knows how cancer works:
“Destroying healthy tissue and clogging vital passageways, metastases are what make cancer deadly”
“… tumors are not just homogenous balls of bad cells. Rather, they are composite tissues, with cancerous and normal cells coexisting in a complex society. But the malignant cells are the ones running the casino.”
“They are Cells Gone Wild. They are defiant, disobedient, unstable, chaotic, and in the view of many cancer biologists, almost purposeful in the ways they disrupt cellular biochemistry.”
She goes through the stages of cancer development in detail, noting the three overlapping stages: initiation, promotion, and progression and how contaminants may affect each stage. More recently two processes: chronic inflammation and abnormal epigenetic regulation have been implicated in transforming cells. Obesity can increase chronic inflammation. Genes affect one’s ability to get cancer and so too does the environment. It is not one or the other but how the two interact. Environmental epigenetics is a new avenue of research investigating how contaminants affect epigenetics, the switches that turn genes off and on or otherwise code them. Oddly, she notes that the Inuit people of Greenland, via their own food chain and the way airborne contaminants have fallen on their region due to weather patterns (called global distillation in terms of contaminant transport) have the highest levels/body burdens of POPs -persistent organic pollutants.
She mentions studies of adoptees and ‘epigenetic drift among twins (the notion that as twins separate geographically that their epigenetic factors change). She is an adoptee and wishes she had access to her genetic history. She thinks the reverse may happen among adoptees – that their epigenetic factors converge with non-adopted siblings due to similar environmental factors. One study among identical twins in Scandinavia suggested that the chance of developing the same cancer as one twin by the other was 11-18%, which shows that genetics is a factor but not as strong a factor as expected, A recent Johns Hopkins study has suggested that cancer is so complex that determining the primary “cause” of most cancers is simply not possible. While cancer may be initiated by accumulations of genetic errors it seems more recently that abnormal regulations of genes by epigenetic factors is the reason. She notes that the Human Genome Study has revealed that we have less genes than thought before the mapping was done but more of those genes are implicated in cancer development than previously thought. She cites the Swedish Family-Cancer Database – the largest dataset of that kind in the world, suggests that family history of cancer plays a modest role in cancer development. She talks about oncogenes and adductors and an enzyme-based chemical detoxification process called acetylation as being factors in the likelihood one would develop cancer – if exposed to carcinogens, particularly early in life. People that are “slow acetylators” are more susceptible and that includes more than half of Europeans and Americans.
She compares a U.S Dept of Health and Human Services brochure to a Genetics textbook regarding the environmental factors of cancer development. The textbook considers environmental factors including smoking, lifestyle habits, and obesity, to be responsible for most (as much as 90%) cancers. Is it mainly a problem of behavior or exposure? We now know that one dietary factor – eating more fruits and vegetables – deceases cancer incidence. She thinks focus on behavioral and lifestyle factors tends to hide the environmental roots of cancer. We do know that occupational exposures, typically more than exposures among the general population to certain contaminants has led to increased cancer rates. She asks whether the obesity factor is also related to greater retention of pollutants, presumably along with greater levels of chronic inflammation. Epidemiologists have cautioned against attributing cancers to single causes and biomonitoring studies and how toxins interact in the body do suggest that complex causes involving many factors could be at play in most cancers.
She calls for green chemistry and the Precautionary Principle but in several cases the Precationary Principle has proven more harmful than beneficial. For instance, in genetic engineering, biotech, and gene editing, the banning of such process in Europe has led to the banning of them in parts of Africa where people could directly benefit from them through less hunger, better nutrition, and more successful and cheaper farming and food. Synthetic chemicals have done a lot of good in the world. Green chemistry is a good idea but may only be marginally applicable. Natural chemicals can also lead to cancer. There are trade-offs and no easy answers. There are extreme costs to re-organizing society on greener principles and there are unknowns. Its easy to say let’s have green energy now but there are toxins associated with these sources as well and tremendous costs and logistical problems. She favors “alternatives assessments” and I can agree – that we should explore alternatives to toxic solutions when possible. She also favors “full-cost accounting” where the health costs of toxic solutions are added in. Apparently, judging from her recent activism, she favors the Precautionary Principle in banning fracking as well. Fracking has resulted in massive decreases of particulate pollution and carbon emissions and better air quality as well as cheaper energy – all due to replacing coal with natural gas in power plants. That would not have occurred if the Precautionary Principle would have reigned as it has in areas where the process is banned. Most things that involve risk also have benefit and these need to be evaluated intently. There is also what is called “risk perception” which among humans has a very strong emotional component due to our evolutionary neurological development. Perception of risk versus real statistical risk can vary considerably. Uncertainty is often exploited by those who favor avoiding risks and those who favor taking risks. Studies have shown, however, that people are more willing to exploit uncertainty and emotionality to promote avoiding risks. Heart disease is bigger problem than cancer and yet people worry more about cancer, seeing it as more of a risk, perhaps because it is thought that we can reverse heart disease with lifestyle changes more than we can reverse cancer the same way.
Overall, this is a very good book: detailed and honestly written. She has worked hard to understand the issue of the environmental factors in the development of cancers. She is no fool. While I disagree with her anti-fracking activism I do understand and agree with her advocacy for better evaluation of chemicals and her call for more studies of environmental factors in cancer as well as getting rid of the most dangerous of chemicals.