A statistical review by the Louisiana Department of Health and the Louisiana Tumor Registry shows some cancer rates in the Cow Island area to be higher and some to be lower when compared to similar cancer rates in Vermilion Parish and throughout the state.
A comparison among three zip codes in the region, including the zip code in which Cow Island is located, showed no consistent pattern of higher rates for arsenic-related cancers.
In a meeting Thursday in Cow Island, Dr. Raoult Ratard, state epidemiologist, said the overall conclusion is there is no statistical difference for the overall combined cancer rate in Cow Island when compared to cancer rates at the parish and state level.
The review was conducted after Cow Island residents raised concerns that arsenic in private water wells in the area might cause cancer. Testing by the Louisiana Department of Environmental Quality in 2004 showed that of 25 water wells sampled in Cow Island, four were found with levels of arsenic above the U.S. Environmental Protection Agency’s limit of 10 parts per billion (ppb).
The Tumor Registry provided LDH with 10 years of cancer data from Vermilion Parish, focusing on three zip codes in that region, one of which was Cow Island. The data were used to compare the parish rates to state rates and to compare the three zip codes’ rates with each other.
“In summary, the cancer data reviewed showed that there was no increased cancer risk that could be linked to arsenic in Cow Island’s drinking water,” said Ratard.
The review also noted no significantly higher rates overall when studying the types of cancer associated with arsenic exposure --- urinary bladder, kidney and liver.
Cow Island Environmental & Health Concerns
Comparison of cancer rates between Vermilion Parish and the state of Louisiana showed:
- no significant difference for all cancer sites combined;
- no significant difference among all four race-sex population groups (white male, white female, black
- male and black female) including all sites combined and cancers associated with arsenic exposure;
- a significantly lower rate for urinary bladder cancer in white males;
- a significantly higher rate for both prostate cancer in white males and lung cancer in black males; and
- no significant difference for other cancers linked to arsenic exposure such as kidney and liver
- A comparison among three zip codes in the region, including the zip code in which Cow Island is located, showed no consistent pattern of higher rates for the cancers of concern.
- In summary, the cancer data reviewed showed that there was no cancer, which could be linked to arsenic in Cow Island’s drinking water. However, these results cannot be used to demonstrate the absence of an environmental public health problem. Obviously, the presence of arsenic levels higher than 10 parts per billion (ppb) in private water wells needs to be addressed.
- Arsenic occurs naturally in rocks, soil, water, air, plants, animals and cigarettes (1.5 micrograms per cigarette). Everyone is exposed to naturally occurring background levels of arsenic.
- Current estimates are that inorganic arsenic exposure of the U.S. population is about 10 micrograms per day, with a range of 0.5 to 125 micrograms per day.
- As with all chemicals, the dose determines if arsenic will cause health effects. High doses are associated with acute toxic effects. With low doses, repeated and/or long-term exposure may be needed, but the health effects of low doses (less than 100 micrograms per day) are not very clear.
- Studies have shown , at doses of arsenic around 200 micrograms per day, arsenic is associated with higher rates of cancer, particularly skin (other than melanoma), urinary bladder, kidney and lung. Liver and prostate cancers were elevated in some studies and not in others.
The level of arsenic in municipal drinking water was set at 50 micrograms per liter or 50 parts per billion (ppb) in 1942 and has been recently lowered to 10 micrograms per liter.
- Of the 25 water wells sampled in Cow Island by the Louisiana Department of Environmental Quality (LDEQ), four were found with levels of arsenic above the U.S. Environmental Protection Agency’s limit of 10 parts per billion (ppb). The levels above 10 ppb ranged from 45 to 60 ppb.
To investigate the concerns about cancer rates, data from the Louisiana Tumor Registry (LTR) were used to both compare Vermilion Parish rates to state of Louisiana rates and the rates from three zip codes in the region (one including Cow Island) with each other.
These types of comparisons are useful to identify effects in large populations; however, they are not precise enough to detect small changes in cancer rates that involve only a few people.
The Louisiana Tumor Registry (LTR) “has submitted five years (1996-2000) of data and passed rigorous criteria for each year’s data including completeness of reporting, non-duplication of records, percent unknown in critical data fields, percent of cases registered with information on death certificates only, and internal consistency among data items” (American Cancer Society, Cancer Facts and Figures 2004). Only 26 states met this high level of quality in 2004.
Demographic and cancer information provided to the Louisiana Department of Health (LDHH) by the residents of Cow Island on 270 community members is being reviewed by the Louisiana Tumor Registry (LTR) and Louisiana Office of Public Health (LOPH) to confirm how many self-reported cases matched those in LTR’s database.