Ragweed pollen is one of the main causes of allergic rhinitis, the seasonally recurrent bouts of sneezing, nasal congestion and itchy eyes commonly called hay fever. There is also some evidence that allergenic pollen can trigger asthma attacks; in Detroit, the asthma rate is 50 percent higher than the rate for the state of Michigan as a whole.
In Detroit, vacant lots are most common in low-income neighborhoods that have large minority populations. Katz and Carey say the results of their land-use study suggest that local production of ragweed pollen disproportionately affects such communities, which raises questions about environmental justice.
The U-M studies found that vacant lots are the main habitat for ragweed in Detroit: Ragweed densities were six times higher in vacant lots than at locations around occupied homes in the city.
Vacant lots contained up to 42 ragweed plants per square meter. When you consider that the tiny, drab flowers of a single ragweed plant can produce up to a billion pollen grains annually, it's clear that Detroit vacant lots are pollen factories churning out a noxious product that afflicts thousands of city residents.
The vegetation survey looked at 62 vacant lots in several neighborhoods, including Mexicantown, Kettering and Core City. The researchers categorized each lot by mowing frequency: monthly, annually, biennially or unmowed.
They found that 28 percent of the unmowed lots contained ragweed plants, while 63 percent of the annually mowed lots and 70 percent of the biennially mowed lots contained the weed. Vacant lots mowed at least once a month during the growing season had no ragweed plants.
"When these lots are left alone comp
|Contact: Jim Erickson|
University of Michigan