Sanitarians also inspected the houses of the 10 cases and four control homes for asbestos, formaldehyde, household chemicals and other sources of indoor pollution. County air pollution officials later measured ambient levels of carbon monoxide from the highway traffic.
They found nothing, county officials say, that could account for the cancers.
Next, the state Department of Health Services did a case-control study, comparing the cancer victims to a healthy control group. Parents were questioned at length about their children's medical histories, habits and hobbies, as well as their own lives and jobs.
The state also looked into pesticide use around McFarland, relying on the reports applicators and farmers must file on certain pesticides. They concentrated on 1980 and 1981--the period when, they figure, something in the environment could have caused the cluster.
Initially, four pesticides caught their attention: They had been used heavily during the potentially critical 1980-81 window. One member of the scientific advisory panel strongly suspects those chemicals; but Neutra said further study of their effects suggests they probably could not be the cause.
A second striking finding was that 80% of the fathers of children with cancer, compared to 45% of the fathers of healthy controls, had worked in the fields during the period between shortly before their child's conception and his or her diagnosis.
To pursue that lead, health officials intend to re-interview the fathers. Sanitarians will tour their workplaces, looking for clues as to how they or their children might have been exposed to chemicals at work that might have been transported home.
The state is also expanding the study: It is collecting data on childhood cancers in all four counties of the southern San Joaquin Valley. If the McFarland cluster is too small to pinpoint a precise cause, officials hope they might find it by looking further afield.
A finding of a high childhood cancer rate regionwide might suggest a problem endemic to farming communities, perhaps related to chemicals, investigators say. Additional cases would then be added to the study group for a larger, maybe more revealing, case-control study.
A finding of no excess cancers in the four-county area, on the other hand, could be something of a dead end.
"I'm not sure what one would have to do next, if the problem appears to be unique to McFarland," said Haile of UCLA. "Launch even more exhaustive studies in McFarland in hopes of finding something, knowing full well that the odds are against you?"
Meanwhile, the protracted uncertainty has shattered the town. Connie Rosales, among others, believes the county and state, at least initially, dragged their feet. Rosales said she is "not conspiracy-minded." But she does not underestimate the power of agriculture, property values and status quo in the public debate.
Though her son survived, she said she has been left with little. She said she is broke, her marriage has ended and she is unable to get work--a fact she traces in part to her bitter feud with the farm workers' union over what she charges is its exploitation of the cancer issue.
The union, she alleges, has used McFarland's misery to raise national support for its boycott of non-union grapes--a cause she does not support. At the same time, she said the union has offered little financial or medical help to the children and their families.
Some of the parents have left McFarland. Others say they would go but they cannot afford to make the move. Some have felt ostracized by the community, haunted by the loss of their children, obsessed with preserving the health of those who remain.
"Our goal is to never have this happen again," said Rosales, who with other parents is suing various agencies, officials and chemical manufacturers.
Active in Community
On the other side of town, Arturo Munoz lays considerable blame with the media. They are killing the town, he bitterly complains. They have singled out McFarland, branding it with a problem that, if it exists, exists throughout the San Joaquin Valley, he said.
Munoz, 66, came to McFarland 45 years ago as one of the first Mexican residents. He has raised seven children, served on the City Council, been active in his church. The reports about the cancer are a blight on his high hopes for McFarland's future.
He wants the press and politicians to leave health officials alone and let them explain the cancers. If there is a problem, Munoz is confident that government and science can fix it. Most of all, Munoz wants the issue resolved and his town left in peace.
What irks Ronald Huebert, the schools superintendent, is the steady ebb and flow of politicians, union organizers and others--people who Huebert says announce their presence with a press release. He calls them "human tornadoes": They blow in, do their damage and leave.