Cancer Cluster Probe Focuses on Dozen Pesticides
After two frustrating years of investigation, scientists report they have found new leads in their search for what may be causing the tragic numbers of childhood cancers in the small San Joaquin Valley farming town of McFarland.
Over the last decade, at least a dozen children have come down with the disease in the Kern County community of 6,500 people, which is 20 miles north of Bakersfield. Six of the children have died.
Digging through statistical files, a task force of county and state health workers has discovered dramatic increases in fetal and infant mortality rates in the community during a three-year period beginning in 1980. Combined with the increased number of cancers and an unusual number of low birth-weight babies, the sharp rise in death rates suggests that something may have been poisoning the environment during that time, according to a consultant to the task force.
The task force’s search for possible contaminants is now focused on a dozen pesticides that, according to Kern County agricultural records, were heavily applied to croplands surrounding the town between 1980 and 1983.
“We’ve looked at all the pesticides (used in the area over the three years) . . . and have narrowed the search . . . to the most heavily used . . . to about 12,†said Dr. Ray Neutra, California Department of Health Services epidemiologist directing the McFarland investigation.
Neutra would not name the suspected pesticides, saying health experts are just now compiling all of the toxicology test data on these chemicals and investigating their application patterns to see if any of the victims or their families could have been exposed during the three-year “window of exposure.†A report on the findings is expected next month, he said.
Experts agree that, while random chance could explain a childhood cancer rate that is four or five times higher than would be expected in a city the size of McFarland, there is also a probability that some environmental aberration could be causing the tragic situation.
Attempts to pinpoint the cause of such a cancer cluster is always a complex, often impossible task. Scientists conducting such epidemiological studies must closely examine the community and its surrounding environment, sorting through the physical, social, economic and cultural history of each family involved, trying to find factors that could link the cases.
Complicating the McFarland study is the fact that nine different kinds of cancers have been found in the children.
At first, investigators were baffled by this. Then Beverly Paigen, a consulting biochemist, suggested that the different types of cancers might be explained by a process called somatic recombination, a change in genetic chemistry that can be triggered by a toxic agent.
Paigen, a geneticist and toxicologist at Children’s Hospital in Oakland, explained that genetic research has shown that when the chemistry of a single gene has been altered, it is possible that different kinds of cancers may be caused by that mutation. Several of the cancers in the McFarland cluster might be explained in this way, she said.
Several Kinds of Cancers
The McFarland victims range in age from under 2 years to 15. The types of cancers include leukemias, Wilms (kidney) tumors, an osteogenic (bone) sarcoma, a neoblastoma involving nerve tissue and two different kinds of tumors of the muscle tissue.
“She may be onto something,†Neutra said. “There is some suggestion that certain kinds of eye and bone cancers have some common genetic route,†Neutra added, but warned that there is no evidence yet to show that this is the case in McFarland.
The McFarland cancer cluster--the first of several that have been identified in the San Joaquin Valley--came to light in 1985 when parents of the cancer victims complained publicly that county and state health officials had ignored their pleas for help. The parents believe that as many as 30 children have come down with the cancer, a number questioned by health officials.
Following the parents’ complaint, the state health department granted $40,000 to Kern County to begin the investigation. Health teams began testing the water, soil and air for contamination. The cancer victims’ families were interviewed and 10 were selected for the epidemiological study, officials said.
Almost from the outset the study ran into problems. Anxious parents complained when the county didn’t include more cases. A county health worker, Thomas Lazar, who compiled a preliminary draft report on the McFarland cluster, charged that his supervisors were ordering him to cover up evidence that pointed to toxic well-water pollution. Lazar, a health educator with a doctorate in anthropology and master’s degree in public health, resigned.
In late November, Mario Bravo, 14, became the sixth victim of cancer, and parents were again complaining that the state-funded study was far behind schedule and had produced no results.
Lazar, now an environmental consultant to the United Farm Workers union, went to the media, claiming that 1983 records show high levels of arsenic in a well drilled that year. He said families living in the McFarland neighborhood plagued by cancer are now suffering from rashes, headaches and “classic chronic arsenic poisoning symptomology.â€
To demonstrate his point, Lazar two weeks ago took one family of four to Dr. Sadegh Salmassi, a Delano physician, who confirmed that the woman and her three children had elevated levels of arsenic in their blood. However, Salmassi said the levels detected were well below toxic levels.
“We heard of Lazar through the press,†Neutra said. “He was asking for chemical analyses of wells . . . and implying there had been a cover-up of major (arsenic) exposure to community . . . (but) there is no evidence that the cancer cluster could be explained by arsenic in the drinking water,†Neutra asserted.
Pointing out that most of the cancer cases had already been diagnosed before the drilling of this one well in 1983, Neutra said records do show that water from the new well initially contained 0.07 parts per million of arsenic. No more than 0.05 ppm are allowed by law. It is not uncommon for new wells to show higher levels of the naturally occurring arsenic, Neutra said, adding that by the time the well was providing water to residents in 1984, the arsenic levels were below the safe limit. There is no evidence that the city’s water supply is contaminated by unsafe levels of arsenic, he said.
The most recent cancer death and the arsenic controversy once again focused media attention on McFarland. Leading Democrats accused the Deukmejian Administration of under-funding the cancer investigation and asked the governor to provide bottled water for all families in McFarland. The Administration earlier this month authorized another $200,000 for the McFarland study.
Out of the most recent episodes has emerged evidence that arsenic may be present elsewhere in the environment. Neutra said some families in the community are suffering from rashes, cramps and diarrhea, possibly from arsenic exposure.
“We may have stumbled onto another public health concern here, but we don’t think it is related to the cancer cluster,†Neutra said. He ordered county investigators back into McFarland to comb the area for possible sources of contamination.
Arsenic, which has been linked to cancer in both laboratory animals and humans, is used in some pesticide formulations applied to cotton and grapes, officials said. Health teams found that the family examined by Salmassi lives within 25 feet of cotton fields. Neutra said, “We’re checking now to see if those fields were treated with monosodium arsenate.â€
The search for the cause of this family’s arsenic exposure has led to the discovery of new potential sources of environmental contamination that could have affected the neighborhood where many of the cancer victims live, said Vern Reichard, Kern County environmental health expert.
The quiet, tree-lined subdivision of modest, relatively new homes lies east of California 99 and the railroad tracks, just beyond rows of old warehouses and sheds. Many of these buildings are now abandoned; several were used to store pesticides, Reichard said.
Empty Drums Found
“We found some old, empty (pesticide) drums in and around some of these buildings,†Reichard said in a telephone interview. Some of the drums contained residues of “sodium arsenate . . . (and) other chemicals more toxic than that,†he added. “We are in the process of identifying the residues and will take some action.â€
Investigators also found traces of the pesticide DBCP (1,2-dibromochloropropane) in well water near the subdivision, Reichard said. DBCP, once a widely used soil fumigant, was banned a decade ago because it caused cancers in laboratory animals.
“The presence of DBCP makes the folks there anxious, and us too. . . . That well and the sump around it are adjacent to the subdivision,†Reichard said. “ . . . Kids were playing there (in the sump) and had to be chased out lots of times.â€
Referring to both the empty drums and the traces of DBCP in the one well, Reichard said: “We don’t know whether or not there is a direct correlation (to the cancer clusters). . . . This is like a giant puzzle; the pieces are steadily coming in and we have to investigate every little piece.â€
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