Research study links more than 200 diseases to pollution
Read the article and download the database on the pollutants and diseases
15.04.2005 |Sascha Gabizon
For example, Childhood Leukemia links to:
- Benzene+,
- Ionizing radiation+,
- Pesticides,
- Metal dusts,
- Chlorinated solvents: carbon tetrachloride, and trichloroethylene (TCE),
- Electromagnetic fields,
- Hazardous air pollutants/Vehicle exhaust,
- Insecticides (chlordane, dichlorvos, propoxur)
- Radon
Summary of the study on 200 pollutants and diseases
Chemical Contaminants and Human Disease:A Summary of Evidence
Sarah Janssen MD, PhD
Gina Solomon MD, MPH1
Ted Schettler MD, MPH2
Human disease results from complex interactions among genes and the environment. Chemical, physical, and biological agents may cause or otherwise influence the onset of various illnesses or disorders in susceptible individuals. Nutritional status and socioeconomic conditions also alter disease susceptibility. Personal lifestyle factors, such as diet, smoking, alcohol use, level of exercise, and UV exposure, are often the primary focus when considering preventable causes of disease. However, exposures to chemical contaminants on the job, at home, in the outdoors, and even in utero are increasingly recognized as important contributors to human disease. These exposures are the focus of this project.
Toxic effects of chemical agents are often not well understood or appreciated by health care providers and the general public. Some chemicals, such as asbestos, vinyl chloride and lead, are known to cause human disease. Other studies suggest that increases in the incidence of some cancers, asthma, and developmental disorders also can be attributed to chemical exposure, particularly in young children. More than 80,000 chemicals have been developed, used, distributed, and discarded into the environment over the past 50 years. The majority of them have not been tested for potential toxic effects in humans or wildlife. Some of these chemicals are commonly in air, water, food, homes, work places, and communities. Whereas the toxicity of one chemical may be incompletely understood, an understanding of the impacts from exposure to mixtures of chemicals is even more deficient. Chemicals may have opposing, additive, or even synergistic effects. In one example of a synergistic effect, tobacco smoking coupled with asbestos exposure increases the risk of lung cancer by 25-fold—a risk much higher than that resulting from the sum of the risks of the individual agents.
The effects of chemical exposures in humans are difficult to study because human experimentation is generally unethical. Therefore, much of the information is gathered from accidental exposures, overdoses, or studies of workers exposed occupationally. Epidemiologic studies in the general population can also be useful though they often have limitations. Many diseases, such as cancer, may not appear until 10-20 years after an exposure has occurred making it difficult for causal associations to be drawn. Exposure assessment, a critical step in environmental epidemiologic studies, is also often difficult. Retrospective exposure assessment usually requires estimates and considerable judgment and is subject to significant error. An individual's exposure may change over time, and exposures often occur to multiple chemicals both in the home and work environments. It is difficult for individuals to remember what they have been exposed to and, moreover, most people are unaware of what their exposures were.
The effects of chemical exposures may vary, depending on the age of exposure (in utero, childhood, adult), the route of exposure (ingestion, inhalation, dermal), amount and duration of exposure, exposures to multiple chemicals simultaneously, and other personal susceptibility factors, including genetic variability. Animal experimentation provides important data about the toxicity of chemicals and adds biological credibility to suspected causal associations in humans.
The Database:
The accompanying database summarizes many links between chemical contaminants and about 200 human diseases, disorders, or conditions. We have designed this database to reflect the current state of knowledge about toxicants and human disease, organized by disease categories. Although the database focuses mainly on specific diseases, some clinical symptoms also have been included where clinical knowledge is lacking. For example, few chemicals are directly associated with the clinical syndrome of attention deficit hyperactivity disorder, but a larger number are associated with decreased attention span.
Data were obtained from three major textbooks on the topic of Environmental Medicine and Toxicology. These sources are:
- Klaassen CD, Ed. Casarett and Doull's Toxicology: The Basic Science of Poisons, 6th ed. (2001) McGraw-Hill publishing, New York .
- LaDou J. Ed. Occupational and Environmental Medicine, 2nd Edition (1997) Appleton & Lange, Stamford , CT
- Rom WM, Ed. Environmental and Occupational Medicine, 3rd edition (1998). Lippincott-Raven, Philadelphia , PA.
The database is designed in Microsoft Excel and is sortable by organ system categories. For example, if someone is interested in oncology, the diseases can be sorted by “onc”. The database can not be sorted by chemical names, but individual chemicals can be located by using the “find” function in Excel.
The major organ systems covered are:
- Cardiovascular (C.V.); Endocrine (endo); Gastrointestinal (G.I.);
- Genitourinary (G.U.); Hematology (Heme); Immunology (Imm);
- Liver (Hepat); Musculoskeletal (msk). Neurology (neuro); <>Respiratory (Resp); Renal (renal); Skin (Derm);
- Allergy (allerg); Development (develop); Geriatrics (geriat);
- Men's Health (male); Metabolism (metab); Oncology (Onc); Otolaryngology (ENT); Pediatrics (Peds); Psychiatry (Psych).
- Women's health (female);
The three columns to the right of each disease or disorder list the corresponding categories as noted above by the abbreviations in parentheses. For example, uterine cancer is placed in the categories of oncology (onc), genitourinary (G.U.), and women's health (female). References for and notes on each condition are found in the far right columns.
Strength of Evidence:
Chemicals that have been linked to a condition are placed in one of three categories based on the strength of evidence for the association.
The "strong evidence" category is reserved for chemicals where a causal association to disease has been verified. The toxicity of these chemicals has been well-accepted by the medical community and are noted in textbook references as, "It is well known that x chemical causes y condition" or "There is strong evidence that x compound causes y disease". Other chemicals were put into this category by causal associations drawn from more recent large prospective or retrospective cohort studies. Finally, chemicals listed as Group 1 human carcinogens by the International Agency for Research on Cancer (IARC) are included in this category. These are chemicals that have been determined to have sufficient evidence for causing cancer in humans.
The "good evidence" category is for associations of chemicals and disease drawn from smaller epidemiological studies (cross-sectional, case-series, or case-control studies) or for chemicals with some human evidence and strong corroborating animal evidence of an association. The strength of these associations is assumed from the texts where no indication of a causal association in human studies was made. IARC Group 2A chemicals, those with limited evidence for causing cancer in humans and sufficient evidence in experimental animals, also are included in this category.
The "limited/conflicting evidence" category contains chemicals that have been weakly associated with human disease by reports from only a few exposed individuals (case reports), or from conflicting human epidemiological studies that have given mixed or equivocal results. In some cases, reports demonstrating toxicity in animals were used but the animal toxicity literature was not comprehensively reviewed. Also included in this category are IARC Group 2B chemicals and EPA Group B2 chemicals. These chemicals show limited or inadequate evidence of causing cancer in humans and limited animal evidence of causing cancer. Many of these chemicals in this category were found in the studies published since the textbooks were last updated.
The majority of the chemicals in the database fall into this limited evidence category. This is because, as noted above, human epidemiological studies are very complex and difficult to design and interpret. Exposures to mixtures of compounds, such as pesticides or solvents, can provide hints of possible associations with disease and direct future research efforts but often cannot provide strong evidence of causation. Most toxicity research is conducted in laboratory animal or test tube (in vitro) studies. Often, human epidemiologic studies are conducted only after an association has been hypothesized, based on other sources. As more scientific research is done some chemicals in the database may be found to have stronger evidence for causing disease, new chemicals will be added, and others may be found to have no association with a disease and fall of the list entirely.
---------- press coverage -----------
14 November 2004
London Independent
US study links more than 200 diseases to pollution
By Geoffrey Lean, Environment Editor
14 November 2004
Pollution has been linked to about 200 different diseases, ranging from cerebral palsy to testicular atrophy, as well as more than 37 kinds of cancer, startling US research shows.
The study, which the authors say probably underestimates the full toll of the contamination, will focus attention on the need for information on the tens of thousands of chemicals routinely released into the environment.
But Britain has weakened the proposed European Union regulations to provide safety information on the substances at the behest of the US government.
The research, by doctors at what was then the University of California and at the Boston Medical Center, was restricted to listing only effects that had been found by several different studies and which are often well known.
More than 120 diseases have been definitively linked to pollution, and in another 33 evidence of a link is judged to be "good". For the rest the evidence is "limited".
Nine different pollutants have been "verified" to cause asthma - including four from car exhausts, the subject of an Independent on Sunday campaign - the study shows. Testicular atrophy is caused by oestrogen, increasingly found in British rivers that supply drinking water. Mercury poisoning can cause cerebral palsy, while more than 50 pollutants - ranging from dioxins to PCBs - have been shown to cause cancer.
Other effects include: kidney disease, heart disease, hypertension, diabetes, dermatitis bronchitis, hyperactivity, deafness, sperm damage and Alzheimer's and Parkinson's diseases.
One of the authors, Dr Ted Schletter of the Boston Medical Center, said yesterday: "The human body is in constant conversation with this chemical milieu and some substances have turned out to be important contributors to disease." He said pollution often acted in concert with genetic predispositions to developing particular illnesses.
Dr J Peterson Myers, chief executive of the Virginia-based Environmental Health Sciences, said because science continued to find new effects of pollution, the number of diseases linked to it was "very much higher".
At the last count - more than 20 years ago - more than 100,000 chemicals were in use in Europe. Few have been properly tested.
Blood tests in the UK, the rest of Europe and the US indicate that most people carry potentially hazardous chemicals in their bodies.
The European Commission has been trying to introduce a new directive requiring industry to provide safety information on the 30,000 most common chemicals, but this measure has been watered down because of pressure from the Bush administration.
A leaked cable signed by Colin Powell, the US Secretary of State, complains that the measures "would be significantly more burdensome to industry and government" and would "impact" on US exports to Europe. Tony Blair, President Jacques Chirac of France and Chancellor Gerhard Schröder of Germany wrote a joint letter to the Commission and succeeded in weakeningthe measure.
