In recent weeks The Sacramento Bee has run several front-page stories regarding a Sacramento resident of the Calvine/Florin area who suspects that there may be a cancer cluster, specifically childhood leukemia, in her neighborhood.

As a result of these stories there has been a good deal of concern in our community that there may be a dangerous situation in our county. 

For your information, there is no evidence at this time that there is any unexpected increase in cancer in that neighborhood.  There is also no evidence that at any time in the past 12 years the residents of that area have been exposed to any increased concentration of carcinogenic agents in the water.

Residents are concerned that there may be an unusual number of childhood leukemia cases in their neighborhood.  They base their concerns on the fact that there were two children diagnosed with leukemia who lived on the same street in 1995. In addition, an adult living nearby had non-Hodgkins lymphoma diagnosed in the same time period.  According to The Sacramento Bee, two more children living on or near that street (one in 1998 and another this year), have also been diagnosed with leukemia. In addition, residents say that over the past 11 years nine more children and one adult have been diagnosed with leukemia in that neighborhood. 

According to The Sacramento Bee, there have been 15 cases of leukemia or lymphoma diagnosed in people who live in that neighborhood or people who have resided at some time in their lives in that neighborhood.  The California Cancer Registry, which performs cancer surveillance for California and deals with these issues, has performed two analyses of the data at citizens’ request. The latest analysis, in June 2002, did not show an increase in leukemia cases expected in the census track to which Auberry Drive belongs.  However, Ms. Dee Lewis believes that the Cancer Registry does not have all the cases she has, and that in addition, they are not looking at cases that lie outside the census track in question.

There is also pressure to count cases of former neighborhood residents that were diagnosed while they lived elsewhere.

Sacramento County Public Health has received telephone inquiries from community members since this story broke. They are concerned about the safety of that neighborhood.  We have told them that at this time there is no evidence that there is an increase in childhood cancer in that neighborhood, nor is there any evidence of any type of increased environmental hazards in that neighborhood. 

Technical Information Relevant to the Situation in Calvine/Florin

The calculation of cancer incidence requires a case definition. According to the California Cancer Registry, a case is defined as a diagnosis confirmed by appropriate laboratory and pathological studies.  The geographic assignment of a case is made based on where a person resides at the time that the diagnosis is made.  The incidence is calculated by the number of diagnoses made in a census track in one year divided by the number of people living in that census track that year.  If one picks a target that covers more than one census track, then the number of cases has to be divided by the number of people living in all the census tracks involved.  One cannot just draw an arbitrary circle around a presumed “cluster” and then divide the number of cases found by just the people living in that circle.  If this were done we could find multiple spurious “clusters” throughout every community in the nation.

Including people whose diagnosis of leukemia was made after they left the Calvine/Florin area will be difficult to justify statistically. If these people are included, then everyone else who lived in that area and then left would also have to be included in the denominator: a number impossible to calculate accurately.

Cancer is much more prevalent than most of us realize. Over our lifetime, 30% (one out of every three persons) of us will get cancer in one form or another. Acute lymphocytic leukemia (ALL) is the most common cancer of childhood, and has been on the increase in the past 20 years.  The causes of childhood leukemia are unknown.  There is an association between having x-rays during pregnancy and subsequent leukemia in children born of that pregnancy. Also, Caucasian and Hispanic children are much more likely to get leukemia than children of other races.   A good epidemiological review of childhood leukemia and information about cancer clusters can be found following the links below.

There has been an association between certain chemical agents and leukemia. These associations have been detected because of increases in leukemia incidence among people who are either occupationally or industrially exposed to these agents.  Among the chemicals implicated in this way we can count, 1,3 butadiene, benzene, carbon tetrachloride and formaldehyde.  Perchloroethylene (PCE) has also been implicated in causing leukemia.

The Sacramento Bee reported that two wells in the area were closed last year because high levels of PCE were found in them. These wells were among the many sources of water for the neighborhood. There is no evidence that the water from these wells, mixed in with water drawn from other sources, ever caused the levels of PCE in tap water to be above the acceptable range. The wells were closed preventively, not as an after-the-fact event.