By Shubert Ciencia

The Clinic is an ongoing collaboration between the Program on Reproductive Health and the Environment at UCSF, Mission Loc@l and UC Berkeley’s Graduate School of Journalism. Prescriptions is a blog about health written by scientists at the Program on Reproductive Health and the Environment at UCSF.

As a child growing up in the 1960s, even middle-class families considered strawberries a pricey, seasonal luxury. In fact, I was happy to have strawberry jam with my peanut butter sandwiches. When I was lucky enough to taste a fresh strawberry, my tastebuds contracted with intense ecstasy and wanted more. Nowadays, super-sized strawberries are practically year-round and plentiful. No longer modest and consumed in one bite, they are garish and grandiose, even tawdry and tarnished. Beautiful to behold and giving the illusion of wealth, modern-day strawberries may promise more risk than taste, research shows.

Just to set the record straight, I am not against progress.

But as a physician, I have been trained to consider and weigh the risks and benefits of decisions. How do we balance the economic viability of the $2 billion strawberry industry with the potential health risks to our children of the chemicals used to grow conventional strawberries? Are strawberries the poster child for what may be wrong with our current industrialized food system?

The answers lie in examining the extensive use of especially dangerous and numerous pesticides to produce the majority of strawberries in the marketplace. More than 2.1 million acres of California strawberry fields were treated with more than 9.8 million pounds of pesticides in 2008. Pesticides’ adverse effects are not limited to the pests they target. Even low levels of some pesticides have been shown to disrupt human hormonal, neurological and immune functioning. Because of their underdeveloped detoxifying mechanisms and other factors, the most vulnerable humans are the developing fetus, babies and children.

Early development and life exposures to certain pesticides have been linked to birth defects, childhood leukemia, neurodevelopmental problems such as ADHD, adult cancers and Parkinson’s disease. Serious human health effects are very real for those whose lives are affected and forever changed. What makes conventionally grown strawberries sold in the Mission and elsewhere cheap comes at a cost for the people who work in the fields, live or attend school nearby, breathe the local air or drink the water from affected aquifers, and for consumers who eat these favored but fouled fruit.

Fumigants, designed to sterilize the soil before planting, are the most common class of pesticides used with strawberry production.  The fumigant methyl bromide is being phased out because it harms the ozone layer. Incidentally, agricultural health studies have found an association between methyl bromide exposure and risk of prostate cancer, so it is a good thing to have it retired. However, the decisionmakers of the California Department of Pesticide Regulation have decided to replace it with methyl iodide, a known carcinogen, and thyroid and nervous system disruptor, as well as a chemical that causes mammalian miscarriage. They say it will be safe to apply under stringent usage protocols. This decision, however, flies in the face of the agency’s own scientific advisory committee that considered health risks of methyl iodide.

These fruits and vegetables have fewer pesticides. Source: Environmental Working Group

Six Nobel scientists also consider methyl iodide to be an extremely dangerous chemical and opposed its registration by the Bush administration’s U.S. Environmental Protection Agency. High-level industrial exposures have caused brain and nervous system dysfunction. Recent groundwater and air testing one year after methyl iodide was applied to fields in Sarasota, Florida, revealed that groundwater had over twice the level of iodine found in seawater, six times the level found in average freshwater, and 150 times the level normally found in that area of Florida. The same Florida studies show that methyl iodide is not fully contained by the tarps that cover the fields, and that air levels of the chemical exceeded those deemed safe by scientists advising the California Department of Pesticide Regulation.

There are colossal public health downsides to reliance on the present system of intensive use of pesticides, including methyl iodide, for strawberry production. However, right now the public policies that drive what ends up in the stores along Mission Street and elsewhere across the state fail to favor the less toxic methods that don’t poison the air, contaminate the water table or deplete the soil. The farmers markets and stores in the Mission that carry organic fruits and vegetables are helping consumers vote for their health with their hard-earned dollars. Organic strawberries have been shown to be tastier, more nutritious, and have a longer shelf life. But in the short term, organic produce is a more costly option, and public policy needs to make food grown without toxic chemicals available at a price everyone can afford. In the end, buying cheaper, non-organic strawberries is not a good deal for us now or a good investment for future generations.

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  1. I surprised to see Dr. Perron’s article stating that there are 2.1 million acres of strawberries in California. According to the California Strawberry Commission’s 2010 acreage survey, there were approximately 37,610 acres planted in strawberries in the state.

  2. Strawberries are year round because they are grown in different climates at different times of the year. I’m not sure where Dr. Perron found information that organic strawberries last longer – as long as strawberries are kept cold and away from moisture, they have the same shelf life. Both organic and conventional growers use the same materials to prevent mold growth.

  3. Thanks for allowing me to clarify Ms. O’Donnell and for giving us the number of acres of planted CA strawberry fields in 2010

    1) The number of acres TREATED with pesticides is a different number than acres PLANTED, i.e. acres of application vs. acres of cultivation

    2)Here is the link from a Washington State University press release confirming the longer shelf life of organic strawberries:

  4. @Carolyn O’Donnell: Perron may be wrong about there being 2.1 million acres of strawberries in the state, but that just indicates that that pesticide use is even more intensive than her article lets on. 9.8 million lbs of pesticides across 2.1 million acres is 4.7 lbs/acres, but across just 37,610 acres its a whopping 260 lbs per acre. That’s a lot a poison!

  5. The 2.1 million acres of strawberries reflects the number of acres treated with pesticides. Most strawberry fields are treated many times with different pesticides during the year, hence the number of “acres treated” is always higher than the number of acres physically under cultivation.

  6. If you’re interested in learning more about pesticides, Californians for Pesticide Reform and Pesticide Watch are releasing their pesticide policy recommendations for the upcoming administration at a press event on

    Nov 30 at 10:30 am.
    Where: Hayes Valley Farm, 450 Laguna St, SF

    Come out and support healthy alternatives to conventional agriculture!

  7. Thanks for the link to the WSU press release – the Los Angeles Times also reported on this study, with comments from scientists regarding the study’s mixed results:,0,1376399.story

    As for treated vs planted acreage, the state Pesticide Use Reports do not distinguish between organic and conventional pesticides. Many “conventional” farmers use organic-approved pesticides and practices, which makes them not-so-conventional.

    You can read some California strawberry grower stories at

  8. In terms of empirical evidence, the strawberries I’ve bought at farmers markets last much less and softer, easier to bruise than the cardboard large ones that the supermarkets sell for free 99. I mean the spoil quickly, so one must enjoy them faster.

    But yeah – scary stuff about the usage of pesticides. Thanks.

  9. Thank you Dr. Perron, for standing up and writing this. Having already been treated for breast cancer I appreciate the information being given to the public. As a graduate of Agriculture many so called safe and production enhancing practices are now illegal, suspect or under investigation. Consumers need to fight back both at the market with their $$$ and with their pens, ipods and phones. If not heard they need to vote those who have assisted in poor decision making out of office. I often also check to see what is accepted in the EU to assist my decisions, they seem to be currently moving along with more speed than the US at this time on public safety.

  10. Dr. Perron’s thoughtful commentary reflects the increasing understanding by mainstream physicians of the deleterious effects of pesticides on human health and the need to transform agricultural practices to produce nutritious food that is essential to good health while eliminating the toxic burden of chemicals known to pose deleterious environmental and public health effects. For example, over the last decade, the California Medical Association (CMA) has passed a number of policies that reinforce this message, including encouraging hospitals to adopt policies and implement practices that increase the purchasing and serving of food that promotes health and prevents disease, including “food grown according to organic or other methods that emphasize renewable resources, ecological diversity, and fair labor practices.” Other policies, cognizant of the negative impacts of pesticide use on agricultural communities, have called for the strengthening of efforts to protect schools and residential communities from pesticide drift and off-site pesticide movement of the sort associated with the application of methyl bromide, as well as supporting efforts to reduce farmworker exposure to pesticides. These measures have been mirrored by similar health-protective policies regarding food and chemicals recently adopted by the American Medical Association (AMA), that reflect a heightened national awareness among health providers about the need to view the health of our patients in the context of promoting a healthful and sustainable environment.


    Robert Gould, MD
    SF-Bay Area Chapter
    Physicians for Social Responsibility (PSR)

  11. Thank you, Dr Perron on your thoughtful article on the use of pesticides in our food. The ramifications of agribusiness and factory farming on our health and society are overwhelmingly bad.
    I remember the first time I tasted a local organic strawberry; it tasted home grown and not like the wholly unsatisfying cardboard things at the supermarket. Here’s to the health, social, and taste benefits of local organic farms!
    Sabrina Modelle

  12. Thanks, Dr. Perron, for this eye-opening article. The facts are staggering, and it makes you wonder about all the other “invisible” toxins we’ve been consuming in other foods besides strawberries, despite the beautiful and fresh appearance of the treated produce. It’s bad enough that the nutrient content of our soil has been depleted over many years, so we’re no longer getting the same vitamin and mineral benefit as earlier generations did, from natural food sources. Now add in the ingestion of pesticides, and one wonders how we plan to sustain healthy human life.
    I’ll do my part to buy organic…we need these farms to stay financially viable!

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