A new study of California twins with autism strengthens the case that the epidemic that has swept the nation in the past three decades is related to environmental pollution. The damage, its authors suggest, occurs in the womb and during the earliest days of life.

"Increasingly, evidence is accumulating that overt symptoms of autism emerge around the end of the first year of life," say the authors of the study, which was released online July 4 in the Archives of General Psychiatry. "Because the prenatal environment and early postnatal environment are shared between twin individuals, we hypothesize that at least some of the environmental factors impacting susceptibility to autism exert their effect during this critical period of life."

If that conclusion is true, an analysis of Toxic Release Inventory (TRI) data from the six states with Ohio River shorelines show that kids in Indiana and Kentucky are at high risk for autism spectrum disorders.

Industries along an 80-mile stretch of the Ohio from Mount Vernon, Ind., to Hawesville, Ky., reported 166.8 million pounds of toxins released into the environment in 2009. That's more than half the 318 million pounds of TRI chemicals released into the air, water and land by the six states through whose territories the nation's 10th longest river flows.

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'Autism and the Indiana Environment Blog'

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Autism is a neurodevelopmental disorder that impairs children's communication, behavioral and cognitive developments. It is a range of disorders that is estimated to affect one in 110 U.S. children today. The most common are Autistic Disorder, Asperger's Disorder and Pervasive Developmental Disorder-Not Otherwise Specified.
"No cause for autism has been identified, but the new study reinforced the long-held scientific belief that autism susceptibility is inherited."
No cause for autism has been identified, but the new study reinforced the long-held scientific belief that autism susceptibility is inherited. Researchers, led by Dr. Joachim Hallmayer from Stanford University, studied 192 sets of California twins and found identical twins were more likely to both have autism than fraternal twins.

Seventy-seven percent of the identical males and 50 percent of identical females both had autism. Comparable figures for fraternal twins were 31 and 36 percent.

"This is a very significant study because it confirms that genetic factors are involved in the cause of the disorder," Dr. Peter Szatmari, an autism researcher and head of child psychiatry and behavioral neuroscience at McMaster University in Ontario, told the New York Times. "But it shifts the focus to the possibility that environmental factors could also be really important."

While previous studies had estimated the "heritability of autism" to be "about 90 percent," the new study found the "shared environment component" to be larger than the genetic.

"To our knowledge, this study is the largest population-based twin study of autism that used contemporary standards for the diagnosis of autism," the authors wrote. "... The results suggest that environmental factors common to twins explain about 55 percent of the liability to autism. Although genetic factors also play an important role, they are of substantially lower magnitude than estimates from prior twin studies of autism."

The Times article said "experts" have concluded the study marks "an important shift in thinking about the causes of autism."

The study does not identify any particular environmental cause, including pollution, but it does cite other studies indicating "environmental influences" include parental age, low birth weight, multiple births and maternal infections during pregnancy.

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If exposure to toxic chemicals in the womb and early infancy during this "critical period of life" play a role in the development of autism and other developmental disabilities, then children conceived and born on the Indiana and Kentucky sides of the Ohio Valley are among the nation's most at-risk, an assertion suggested by a previous analysis of special education enrollment in Indiana.
"The results suggest that environmental factors common to twins explain about 55 percent of the liability to autism."
In Evansville, Indiana's third largest city, 22 percent of public school children in 2009 received special ed, which serves children with developmental disabilities, including autism, learning disabilities and communication disorders. In the 19 Hoosier counties closest to the Ohio, it was 20 percent. In Posey County it was 26. Statewide the percentage was 17.5.

By federal law, industries that use any of 682 toxic chemicals must account for them once a year to the U.S. Environmental Protection Agency (EPA). The term release means chemicals either escaped from smokestacks into the air; were discharged into rivers, lakes and streams; or were landfilled. 2009 is the latest data reported on EPA's TRI Explorer database.

Among the TRI chemicals are several identified neurotoxins linked to developmental disabilities in children, including aluminum, ammonia, arsenic, lead and mercury.

On a per capita basis, the TRI data show Indiana is by far the valley's largest polluter, releasing 70 pounds of toxic chemicals per person living in 19 counties near the river. Kentucky is second with 55 pounds per citizen, followed by West Virginia with 42, Ohio with 27, Pennsylvania with 24 and Illinois with 13.

Kentucky, which also has the longest Ohio River shoreline, with 41 counties either on the river or one county away, reported the most total TRI releases with 112 million pounds. Ohio was a distant second with 67.4 million. Indiana was third with 54.8 million.

Forty-one of the 123 counties in all six states -- exactly one in three -- reported more than 1 million pounds of toxic releases in 2009. Of the top 10, five were in Kentucky, two in Pennsylvania, two in Ohio and one in Indiana.

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By far the Ohio Valley's largest polluters are located in 13 counties in Southwest Indiana and Northwest Kentucky.
"In Evansville, Indiana's third largest city, 22 percent of public school children in 2009 received special ed, which serves children with developmental disabilities, including autism, learning disabilities and communication disorders."
Thirteen industries in Henderson, a Kentucky county of 45,274 directly across the river from Evansville, reported 35.3 million pounds of 43 separate toxins released in 2009, including aluminum, ammonia, arsenic, lead and mercury. But one coal-fired power plant complex near Robards, operated by the Big Rivers Electric Corp., released 34.8 million of those pounds.

According to its Web site, Big Rivers is a "member-owned, not-for-profit, generation and transmission cooperative (G&T) headquartered in Henderson, Kentucky. We provide wholesale electric power and services to three distribution cooperative members across 22 counties in western Kentucky."

Big Rivers operates five power plants, including three at the same location in Robards, collectively known as the "Sebree station." According to the TRI reports, Sebree released 15 pounds of ammonia, 111,116 pounds of arsenic compounds, 50,930 pounds of lead compounds and 691 pounds of mercury compounds in 2009.

Roughly 40 miles to the east, Spencer County, Ind., ranked fourth, with 20.9 million pounds of TRI chemicals -- 1,037 pounds per county resident. Two facilities located three miles apart -- AK Steel and the American Electric Power's Rockport Power Plant -- accounted for all but 18,740 pounds of the county's releases.

AK Steel released 13.4 million pounds of TRI chemicals, including 11,357 pounds of ammonia and 2,080 pounds of lead.
"Thirteen industries in Henderson, a Kentucky county of 45,274 directly across the river from Evansville, reported 35.3 million pounds of 43 separate toxins released in 2009."
The coal-fired Rockport plant reported releases of 7.4 million pounds, including 52,034 pounds of arsenic compounds, 57,495 pounds of lead and 1,226 pounds of mercury.

Another 20 miles upriver in Hawesville, Ky., Big River Electric's Kenneth C. Coleman Station reported 21 million pounds, making Hancock County the valley's third biggest toxic polluter. Its releases included 70,726 pounds of arsenic compounds, 29,203 pounds of lead compounds and 253 pounds of mercury.

The most studied and understood of the neurotoxins released in the region is mercury. A 2008 report from the U.S. Geologic Survey (USGS) in Indiana found "some of the highest mercury deposition in the U.S." just outside of Madison, Ind.

A historic town known for its 19th century architecture, Madison is 160 miles upwind from the Evansville/Henderson region and 13 miles downstream from Carroll County, Ky., where industries reported releases of 1,192 pounds of toxic chemicals per capita, including 516 pounds of mercury from the Kentucky Utilities Ghent Station power plant.

Madison is home to another coal-fired power plant, the Clifty Creek Station, which released another quarter ton of mercury into the environment in 2009.

"The maps indicate that high annual mercury emissions in the area may be an important factor affecting mercury concentrations in precipitation," the Geological Survey said.

Steven Higgs can be reached a .