Botulism, a rare but serious foodborne illness, continues to be a concern for home canners and public health officials. According to Paige Weisskirch, a volunteer with the UC Master Food Preserver Online Program, misconceptions about safe food preservation practices persist despite scientific evidence.
Weisskirch notes that many people question whether botulism is still a risk due to its low incidence in the United States. Surveillance data shows there was a median of 19 laboratory-confirmed cases of foodborne botulism per year from 2001–2017. However, she emphasizes that these low numbers are due to adherence to science-based safety methods. “The threat is not imaginary or overstated. It is controlled by good practice,” Weisskirch writes.
Botulism is caused by toxins produced by the bacterium Clostridium botulinum when it grows in environments with low oxygen, low acidity, sufficient moisture, and suitable temperatures. The spores are common in soil and water but only become dangerous under specific conditions found in improperly preserved foods.
Symptoms typically develop within 12 to 36 hours after consuming contaminated food and may include fatigue, weakness, blurred vision, dry mouth, and difficulty swallowing or speaking. The toxin attacks the nervous system and can lead to respiratory failure if untreated. Treatment relies on antitoxin administration within the first 24 hours of symptom onset; even so, some patients die from complications such as pneumonia or sepsis.
Despite modern medical care reducing fatality rates from historical levels of up to 50 percent down to about 5 percent today, botulism remains life-threatening because contaminated foods often appear normal.
Prevention remains critical. Safe canning involves multiple steps: selecting quality ingredients, following tested recipes and processing methods appropriate for food acidity and altitude, using correct jar sizes and processing times, ensuring proper cooling and sealing procedures, and storing jars safely. When this process is followed completely as designed by research institutions such as university extension programs—including those offered by UC Agriculture and Natural Resources—botulism cases remain rare.
Weisskirch warns against shortcuts like “dry canning” or boiling low-acid foods without pressure canning. She explains that boiling alone does not reach high enough temperatures to destroy C. botulinum spores in low-acid foods within practical timeframes; pressure canning is required for these products according to guidelines from agencies such as the USDA.
Recent outbreaks illustrate ongoing risks tied to unsafe practices rather than geography. In Fresno County, California in 2024, eight people were sickened after eating home-prepared prickly pear cactus; six required intensive care (ICU) treatment while two needed mechanical ventilation. Similar incidents occurred in Italy and France linked to commercially prepared sandwiches and home-canned carrots respectively—resulting in several deaths.
Public health authorities continue to emphasize that safety comes from validated methods rather than personal anecdotes or tradition: “One person’s uneventful history with a method does not make that method safe,” Weisskirch states.
Organizations like UC Agriculture and Natural Resources play an important role statewide by sharing science-based practices through local offices across all California counties as well as nine Research and Extension Centers operating as living laboratories across diverse ecosystems (source). As part of the University of California system (source), UC ANR delivers expertise through research initiatives focused on nutrition education, sustainable agriculture, environmental conservation, wildfire protection, youth programs—and supports community well-being throughout California (source).
The organization encourages Californians who preserve their own food at home to rely on tested guidelines rather than anecdotal advice or internet trends: “Science-based canning guidelines are the pathway to food that is both safe and shelf-stable…Safe canning practices protect not just the food but the people who will eat it.”