Air pollution damages across generations
Air pollution damages across generations
10 December 2002
Environment News Network (ENN)
Air pollution from steel mills causes genetic damage that fathers can pass to the next generation, researchers in Canada reported Monday.
It is not clear if the genetic damage could harm anyone's health, but tests on mice showed that those allowed to breathe air from near a smoke-belching steel mill had fewer pups and those pups had more genetic mutations than their country cousins.
The findings, published in the Proceedings of the National Academy of Sciences, suggest that steel mill workers and people living near those mills should be checked for damage to their health, said the researchers, at McMaster University in Hamilton, Ontario.
"Our findings suggest that there is an urgent need to investigate the genetic consequences associated with exposure to chemical pollution through the inhalation of urban and industrial air," they wrote in their report.
Christopher Somers, James Quinn, and colleagues did an earlier study that showed gulls living near a steel mill on Lake Ontario had genetic mutations. In this study, they raised two groups of mice one half a mile downwind of the mill and one about 20 miles away.
The mice made to breathe the polluted air had 1.5 times to twice as many mutations in their DNA as the mice breathing fresh country air, Somers and colleagues reported.
Bad air a 'genetic risk' - Mac shows mutated genes hereditary
By Eric McGuinness
McMaster University research is the first in the world to show that urban air pollution causes gene damage which animals pass from one generation to the next.
Biologists Jim Quinn and Chris Somers have demonstrated that male laboratory mice exposed to Hamilton steel-mill emissions transfer mutated genes to their young. And they warn the same thing could be happening in humans.
While gene mutations may increase risk of cancer and birth defects, the McMaster scientists say they can't make a direct comparison to human health.
At the same time, they say there's every reason to believe human genes react the same way.
That creates an urgent need to investigate the genetic consequences of chemical pollution in urban air, especially in places such as Hamilton, where there are integrated steel-making complexes.
Quinn and Somers placed one colony of laboratory mice downwind of the Stelco and Dofasco mills and another in rural Freelton for 10 weeks in the fall of 1999.
They then allowed the mice to breed and tested tail tissue for gene damage.
They found far more mutations in the city mice, mutations that were inherited by baby mice almost entirely from their fathers.
The results appear in the current issue of a respected U.S. research journal, Proceedings of the National Academy of Sciences.
Quinn and Somers blame the genetic damage mainly on polycyclic aromatic hydrocarbons or PAHs -- toxic chemical compounds that attach themselves to microscopic, breathable particles of soot and dust. They say PAHs are among the most genotoxic or gene-damaging urban air pollutants and that steel mills are a major source.
PAHs in the body are thought to attach to strands of DNA, the carriers of genetic information, and are suspected of playing a role in formation of cancerous tumours.
The Mac scientists say their discovery means people working in or living around integrated steel-making complexes -- ones that produce steel from iron ore rather than just recycling scrap -- may be at higher risk of genetic mutations induced by the air they breathe.
"Globally, hundreds of thousands of humans live or work in industrial areas near steel mills and are incidentally exposed to airborne emissions. These populations may be at risk of increased heritable mutation frequency through exposed fathers."
Health Canada experts who co-authored the research paper previously found mutations in herring gulls nesting downwind of the Hamilton mills, but couldn't separate the effects of air and water pollution, so mice were chosen for a followup study.
Although the city mice and country mice were fed identical diets, the mutation rate in city mice was 1.5 to two times than that of their rural counterparts. The city mice also had smaller litters. Quinn and Somers attribute the differences to air quality.
While cars, diesel engines and other industries also emit PAHs, the researchers point to steel mills as the culprit because they produce high levels of the toxic substances and because the earlier gull studies showed birds in Hamilton had more mutations than those in Toronto, a larger city with lots of traffic but no integrated steel-making complexes.
Quinn, 49, is an associate professor of biology. Somers, 28, is a PhD candidate who carried out most of the work with the mice.
Somers says one way to reduce the risk from steel mills would be to better filter their air emissions to remove the tiny particles that carry PAHs. To test that theory, he and Quinn have already conducted a second experiment in which two colonies of mice were placed on Pier 25 on the Beach Strip, half exposed to the air outdoors, half breathing filtered air. Results of those tests should be available early next year.
The genes being studied are prone to mutations and not ones that would directly result in birth defects, but Somers says there's every reason to believe other genes are similarly affected, though at a much lower rate.
Quinn compares the mice with canaries once used to warn coal miners of dangerous gases. The research paper says, "The use of sentinel laboratory animals exposed in situ is a powerful experimental approach for assessing air pollution hazards because it combines the controlled elements of laboratory studies with direct exposure to ambient pollution levels."
Before this, elevated mutation rates were found in human families living near sites of radioactive contamination in Belarus and other former Soviet republics as well as in barn swallows near the nuclear reactor accident site in Chernobyl. But the herring gull and mouse studies in Hamilton are so far the only ones showing chemicals can cause mutations that are inherited.
Source: The Hamilton Spectator (Canada - December 10 2002)
The following are further summaries and sources for further data on this issue, followed by a rebuttal from Dofasco Inc Proceedings of the National Academy of Sciences - Air pollution induces heritable DNA mutations
James S. Quinn, associate professor, McMaster University
The respiratory effects of air pollution are well documented. Now the results of a new study suggest that industrial pollution could cause genetic defects, too. Findings published online this week by the Proceedings of the National Academy of Sciences indicate that mice subjected to ambient air in close proximity to a steel mill had twice as many genetic mutations as their rural counterparts did.
Previous research had shown that gulls living close to steel mills in the Great Lakes region had increased rates of DNA mutations. The exact role of air pollutants was unclear, however, because the birds may have also been exposed to toxins in their water supply. In an attempt to elucidate the effect of air pollution, Christopher M. Somers of McMaster University in Hamilton, Ontario, and his colleagues housed two groups of mice in separate locations for 10 weeks. The first group was situated one kilometer downwind from two steel mills, and the second was placed in a rural setting 30 kilometers away. After being returned to the laboratory, the mice and their offspring were tested for genetic mutations. The researchers found that the mice that had lived near the mills had smaller litters, on average, than did those that lived in the country. What is more, the so-called steel mice exhibited twice as many DNA mutations as the control animals did, with the majority originating from the fathers. The authors conclude that "this is the first demonstration of heritable mutation induction in any organism as a result of ambient air pollution exposure." -- Sarah Graham
Mutagens Are in the Air
The billowing smoke from steel mills may not only make it hard to breathe, but may also cause genetic damage, according to new research in PNAS this week. Scientists have long suspected that industrial pollution poses a significant risk to the health of human and animal populations, although much of the evidence is anecdotal or confounded by factors other than air pollutants. James Quinn at McMaster University and colleagues previously found a high rate of heritable mutations in herring gull populations nesting near steel mills. However, it was unclear whether the observed effect was due to emissions in the air or contaminants in the water. To isolate and examine the effect of air pollution, Quinn and colleagues housed laboratory mice in ambient air 1 km downwind from two integrated steel mills near Lake Ontario and a rural location 30 km away. Mice exposed to air pollution from the steel mills had offspring with a greater number of DNA mutations compared to rural mice. Also, steel mill mice had slightly smaller litters than rural mice. Although the potential health effects of the mutations remain unclear, these findings suggest that some component of industrial air pollution has the potential to cause genetic damage that could adversely affect generations to come.
"Air pollution induces heritable DNA mutations" by Christopher M. Somers, Carole L. Yauk, Paul A. White, Craig L. J. Parfett, and James S. Quinn Published online before print
December 9, 2002, 10.1073/pnas.252499499; Proc. Natl. Acad. Sci. USA, Vol. 99, Issue 25, 15904-15907, December 10, 2002
Air pollution induces heritable DNA mutations - Christopher M. Somers*, Carole L. Yauk, Paul A. White, Craig L. J. Parfett, and James S. Quinn*,
* Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON, Canada L8S 4K1; and Mutagenesis Section, Environmental and Occupational Toxicology Division, Health Canada, Environmental Health Centre, 0803A, Tunney's Pasture, Ottawa, ON, Canada K1A 0L2 Edited by Richard B. Setlow, Brookhaven National Laboratory, Upton, NY, and approved October 28, 2002 (received for review August 19, 2002)
Hundreds of thousands of people worldwide live or work in close proximity to steel mills. Integrated steel production generates chemical pollution containing compounds that can induce genetic damage (1, 2). Previous investigations of herring gulls in the Great Lakes demonstrated elevated DNA mutation rates near steel mills (3, 4) but could not determine the importance of airborne or aquatic routes of contaminant exposure, or eliminate possible confounding factors such as nutritional status and disease burden. To address these issues experimentally, we exposed laboratory mice in situ to ambient air in a polluted industrial area near steel mills. Heritable mutation frequency at tandem-repeat DNA loci in mice exposed 1 km downwind from two integrated steel mills was 1.5- to 2.0-fold elevated compared with those at a reference site 30 km away. This statistically significant elevation was due primarily to an increase in mutations inherited through the paternal germline. Our results indicate that human and wildlife populations in proximity to integrated steel mills may be at risk of developing germline mutations more frequently because of the inhalation of airborne chemical mutagens.
Study Looks at Pollution, Gene Mutations
By Paul Recer AP Science Writer
Monday, December 9, 2002
Washington (AP) - Exposure to air pollution from steel mills may cause genetic mutations that are passed by fathers to their offspring, according to a study in mice.
Ecology scientists at McMaster University in Hamilton, Ontario, Canada, said pairs of mice exposed for about 70 days to air pollution downwind from a steel mill produced young that carried up to twice the number of genetic mutation found in animals that lived in clean air.
Christopher M. Somers and James S. Quinn, two of the co-authors of a study appearing in the Proceedings of the National Academy of Sciences, said the new research supports earlier findings that suggested that genetic mutations among seagulls exposed to steel mill air pollution.
A toxicology expert questioned the study's methods and conclusions. In the study, Somers, Quinn and their colleagues used two groups of 20 mice, half male and half female. One group was placed in a shed six-tenths of a mile downwind from two steel mills in Hamilton Harbor near the western shore of Lake Ontario. The other group was housed in a shed in a rural area 18 miles away.
After 10 weeks of exposure, both groups were returned to the laboratory. Breeding pairs were established randomly within each of the groups. The animals exposed to the steel mill air pollution had a breeding success rate of 85 percent, compared with the 95 percent success rate among the rural mice. Mean litter size for the steel mill group was 7.9 pups per couple, versus 9.6 pups for the rural couples.
After profiling the DNA of the pups, researchers found that the offspring of mice exposed to the steel mill air pollution had up to twice the number of abnormal DNA sequences as the pups from the rural couples. Somers said an analysis showed the genetic changes had been passed to the pups from their fathers.
None of the specific genetic mutations detected would affect development or appearance of the mice, said Somers. However, he said genetic mutations have been linked to cancer and other diseases.
Quinn said the mutations may be caused by polycyclic aromatic hydrocarbons, or PAHs, known to be present in some stack gases coming from steel mills. Steel mills burn coal or other fuels to refine ore or rough metal into steel. He said the PAHs are known to cause mutations and can enter the body by attaching to small airborne particles that are inhaled.
The authors said the study suggests that humans and wildlife exposed to airborne particles "may be at risk of developing germline (inheritable) mutations.''
But "that is a big stretch'' not supported by the data, said Coreen A. Robbins, a consultant for GlobalTox, a toxicology and industrial hygiene company based in Redmond, Wash.
She said confirming studies need to be done before steel mill air pollution can be conclusively linked to genetic mutations. Robbins also questioned the methodology used, noting there was no effort to specifically chemically analyze the air breathed by the animals.
"It looks like from the study that we have no idea what these animals were exposed to,'' she said.
Dofasco Rejects McMaster University Study - Results Speculative and Irresponsible
HAMILTON, ON, Dec. 10 /CNW/ -
Dofasco Inc. today rejected the findings of a McMaster study widely reported in the media linking steel mills and gene damage in mice.
"We dismiss this study as speculative and irresponsible," said John Mayberry, Chair of the Board and Chief Executive Officer of Dofasco.
"This is disappointing. There appeared to be no effort whatsoever to scientifically establish the actual cause of the gene damage among the test mice."
The researchers test site was near the Hamilton Beach Strip, downwind from the entire city of Hamilton, including the industrial core, and adjacent to the Queen Elizabeth Highway, one of the busiest stretches of highway in North America. "There would have been at least 100,000 vehicles passing within a stone's throw of the mice each day over the course of the study," said Mayberry.
Mayberry said he saw no evidence of any effort to isolate sources of emissions. "We saw no evidence of the researchers distinguishing steel mills from other sources upwind of the test site. We saw no evidence of them distinguishing steel mill emissions from vehicle exhaust. We do not believe there were adequate research controls in the study in regards to identifying or distinguishing the potential sources of emissions or their effects."
Further, the study concluded polycyclic aromatic hydrocarbons (PAHs) were the cause of the genetic mutations in test mice. "The researchers isolated this element from other elements found in the ambient air and declared it the cause of the gene damage in mice, but they do not provide compelling evidence or explanation for this linkage," said Mayberry.
A consultant from GlobalTox, an international consulting firm, commented on the issue earlier today. "It looks like from the study that we have no idea what these animals were exposed to," Coreen A. Robbins is quoted as saying.
She went on to characterize the causal relationships of the research findings as "a big stretch." Dofasco encourages academic research that benefits the community.
"We are committed to the well-being of our environment and our community, which is reflected in our performance and through third party validation of our industry leadership. We would welcome and encourage more accurate and thorough research to definitively identify the cause of the gene damage." Dofasco was also highly disappointed in the quality of news reporting.
"While this study received prominent coverage by a number of news agencies, not one news reporter called Dofasco to request our opinion on the study. In our view, the steel industry should have been provided the opportunity to comment," said Mayberry.
Dofasco is a leading North American steel solutions provider. Product lines include hot rolled, cold rolled, galvanized, Extragal (TM), Galvalume(TM) and tinplate flat rolled steels, as well as tubular products and laser welded blanks. Dofasco's wide range of steel products is sold to customers in the automotive, construction, energy, manufacturing, pipe and tube, appliance, packaging and steel distribution industries.NB - There is a response to this press release posted on our site.