At the request of the Santa Cruz County Public Health Officer, the Greater Bay Area Cancer Registry (GBACR) and the California Cancer Registry (CCR) reviewed childhood cancer incidence data in Santa Cruz County from 1988 through 2022. The purpose was to describe patterns in childhood cancer diagnoses and evaluate whether any unusual trends were present.

Pediatric cancer is rare, so these findings should be interpreted cautiously. Public health experts study cancer trends over many years because the number of cases in smaller communities can vary significantly from year to year. This review could not assess whether those with cancer in South County had any exposure to pesticides and cannot establish any causes of these cancers. Cancer registry data can track trends over time, but they cannot determine the exact causes of cancer. Santa Cruz County Public Health will continue to monitor childhood cancer trends with state and regional public health experts.

These findings should be considered alongside existing research regarding pesticide exposure. Several decades of research have already established known links between certain pesticide exposures and increased risk of specific childhood cancers, including acute lymphocytic leukemia, acute myeloid leukemia, lymphoma, and brain cancers. This existing research includes large, long-term studies which are able to directly connect exposures to associated disease.

The analysis used data from the California Cancer Registry, which collects information on cancer diagnoses throughout California. The review focused on cancers diagnosed among children and adolescents ages 0–19 living in Santa Cruz County at the time of diagnosis.

A statewide analysis found that approximately 8,500 California children and adolescents ages 0–19 were diagnosed with cancer between 2017 and 2021.

Cancer is:

• The second leading cause of death among children ages 0–14.
• The fourth leading cause of death among adolescents ages 15–19.

Statewide, acute lymphocytic leukemia (ALL) is the most commonly diagnosed childhood cancer across all racial and ethnic groups.

Over the 35-year study period (1988–2022):

• Non-Hispanic White children generally had higher childhood cancer rates than Hispanic children.
• However, because childhood cancer is rare, there were often too few cases to know whether the observed differences reflected a true difference in risk or were due to normal statistical variation.

Among non-Hispanic White children, childhood cancer incidence increased from 15.1 cases per 100,000 children in 1988–1992 to 29.6 cases per 100,000 children in 2018–2022.

Among Hispanic children, rates remained lower and relatively stable over the same period, ranging from 12.8 to 15.9 cases per 100,000 children, with no clear increasing or decreasing trend.

Yes. During the most recent decade analyzed (2013–2022):

• Non-Hispanic White children had a childhood cancer incidence rate of 25.6 per 100,000 children.
• Hispanic children had a rate of 16.6 per 100,000 children.

This difference was statistically significant. More data is required to determine whether this represents a sustained trend.

Because Santa Cruz County alone had too few leukemia cases for reliable analysis, researchers combined data from Monterey, San Benito, and Santa Cruz counties.

In the combined regional analysis:

• Hispanic children had a leukemia incidence rate of 6.7 per 100,000.
• Non-Hispanic White children had a leukemia incidence rate of 3.9 per 100,000 children.

In the combined regional analysis, leukemia incidence among Hispanic children was significantly higher, with Hispanic children experiencing about 1.7 times the rate observed among non-Hispanic White children. Nationally, Hispanic children and adolescents under 20 years of age are diagnosed with leukemia at rates approximately 1.5 times higher than non-Hispanic White youth (2019–2023), according to the National Cancer Institute and the American Cancer Society.

For the period 2018–2022:

• Twenty childhood and adolescent cancer cases were identified in the South County study area.
• Sixteen cases occurred among Hispanic/Latino children.
• The remaining cases occurred among Asian American, Native Hawaiian, Pacific Islander, and non-Hispanic White children.
• No cases were identified among non-Hispanic Black children.

Overall, the number of cancer cases observed in South County was consistent with what would be expected based on the area's population size and established cancer rates.

For this study, South Santa Cruz County included census tracts 110100, 110200, 110300, 110400, 110501, 110502, 110600, 110700, 122300, 122400, 122500, 123100, and 123300.

Researchers examined selected cancer types that have been studied in relation to pesticide exposure, including:

• Acute lymphocytic leukemia (ALL)
• Acute myeloid leukemia (AML)
• Lymphoma
• Brain and other central nervous system cancers

The analysis found no increase in these selected cancer types in South County compared with the rest of the Greater Bay Area Counties, which also include San Francisco, Alameda, Contra Costa, Marin, San Mateo, Monterey, San Benito, and Santa Clara counties.

No, these analyses were not designed to determine cause. Cancer registry data can identify patterns and trends in cancer diagnoses, but they do not contain information on:

• Environmental exposures
• Pesticide exposure
• Residential history
• Occupational exposures
• Individual risk factors

Because of these limitations, the registry data alone cannot determine whether environmental factors caused or contributed to cancer cases.

Childhood cancer is relatively rare. In Santa Cruz County, the small number of cases results in:

• Wide confidence intervals
• Greater year-to-year variation
• Frequent data suppression to protect privacy
• Reduced statistical reliability

These factors make it challenging to identify meaningful trends or differences within small geographic areas. Furthermore, this data is not able to assess pesticide exposure among those with cancer because it does not include residential history.

Yes. Cancer registry data record a person's address at the time of diagnosis, not where they may have lived previously. As a result:

• Children who moved away before diagnosis are not included in local rates.
• Children who recently moved into the county before diagnosis may be included.
• Potential exposures that occurred elsewhere may not be reflected in local analyses.

This is particularly important when considering environmental or occupational exposures that may have occurred years earlier.

Not necessarily. Many cancers take years to develop, and not everyone who is exposed to a potential risk factor will develop cancer. Because there can be a long delay between an exposure and a diagnosis, and because cancer is influenced by multiple factors, recent exposures may not show up in cancer statistics for years.

The review found:

• Childhood cancer incidence rates in Santa Cruz County are generally consistent with statewide patterns.
• A statistically significant increase in childhood cancer incidence among non-Hispanic White children in Santa Cruz County from 2013–2022.
• Overall childhood cancer rates among Hispanic children remained stable over the study period.
• In the combined Monterey–San Benito–Santa Cruz regional analysis, Hispanic children had higher rates of leukemia, which is consistent with national trends.
• Cancer incidence among children and adolescents in South County was not higher than expected during the 2018–2022 study period.
• No increase in selected cancers associated with pesticide exposure in South County compared with the rest of the Greater Bay Area.

The review also concluded that cancer registry data alone cannot determine the causes of cancer and cannot independently confirm or rule out environmental or pesticide-related factors.

The California Cancer Registry and Greater Bay Area Cancer Registry will continue monitoring cancer incidence trends over time. Ongoing surveillance remains important for identifying potential changes in cancer patterns and supporting public health efforts in Santa Cruz County. County Public Health values this surveillance work and its importance to the health of our community. We will continue to keep our residents informed of any concerning trends or developments.

• Cancer Prevention Starts in Childhood | CDC
• What are childhood cancers? | American Cancer Society

• Department of Pesticide Regulation
• Spray Days California