(Beyond Pesticides, April 10, 2007) Scientists have reported several environmental estrogens can affect the immune system, promoting allergic diseases such as asthma. Researchers have observed this response using pesticides and other environmental contaminants.
Focusing on six environmental estrogens (xenoestrogens), researchers were able to reveal how these contaminants affect the immune system. Using doses representative of present human exposures, these estrogen-mimics were tested on human and mouse cells. The observed effect of exposure was both an increase in speed and intensity of immune reactions.
Three of the environmental estrogens tested were organochlorine pesticides or metabolites: endosulfan, dieldrin and DDE (DDT metabolite). The other contaminants included nonylphenol, a by-product of plastics manufacturing, and two PCBs.
The study reveals that the accelerated and increased level of degranulation of mast cells is the mechanism that causes more severe allergic reactions than would otherwise take place. According to Environmental Health News, mast cells play a vital role in allergic reactions because they are primed by past experience with allergens to release inflammatory agents into the body, which causes an allergic reaction. If the mast cell has been primed to react to a specific allergen, it will degranulate, releasing molecules such as histamine. The more intense the degranulation, the more intense the allergic reaction. Therefore, since environmental estrogens increase degranulation, these contaminants can intensify the strength and even frequency of allergic reactions.
The researchers also found that in combination with endogenous estrogen (estrogen produced within the body), environmental estrogens had an additive effect on degranulation, in effect, amplifying allergic responses.
The researchers state, â€śThis estrogenic impact is likely to be important both for rapid disease-promoting responses, such as mast cell activation, and for more long-term pathogenesis, such as estrogen-induced cancers.”
They conclude, â€śThe results described here indicate that we must also consider the possible impact of environmental estrogens on normal immune function and on the development and morbidity of immunological diseases such as asthma.”
These findings help to explain the dramatic increase of asthma and other allergic diseases that have taken place, especially in industrialized countries, over the past thirty years. Several persistent and ubiquitous pollutants, including pesticides, produce estrogen-like responses and tend to bioaccumulate and bioconcentrate in the food chain. Biomonitoring studies have shown most of us carry around many of these chemicals in our body.
The full study, â€śEnvironmental Estrogens Induce Mast Cell Degranulation and Enhance IgE-mediated Release of Allergic Mediators,” is available in the January 2007 edition of Environmental Health Perspectives.
Muhammed Towhid Salam, M.D., will speak on the link between pesticides and asthma at Beyond Pesticidesâ€™ 25th National Pesticide Forum, Changing Course in a Changing Climate: Solutions for health and the environment, which will be held June 1-3 in Chicago.