Occupational exposure is the most common type of exposure to asbestos. Workers in a variety of industries have respirated or otherwise "taken-in" asbestos due to the presence of the fibers in a number of products. It is because of this fiber intake that certain occupations have higher-rates of mesothelioma and other asbestos-caused diseases than do other occupations. However, on-the-job exposure to asbestos is not the only cause of these diseases. Secondary exposures, known also as bystander exposures, do occur and are a greater source of disease onset than was previously realized.

Bystander exposure occurs in a variety of settings: at home, outside, in a school or place of business, etc. The exposure can take place from coming into contact with a person who was previously exposed and is inadvertently carrying the fibers on his or her clothing, from simply walking through a space with contaminated air because of construction or re-modeling or even walking by an area where asbestos was once manufactured where the kicked-up dust may have significant asbestos contamination.

Mesothelioma: You Do Not Have to Work for it

While bystander exposure has been a known cause of asbestos disease for quite some time, there have not been many formal studies done that attempt to quantify the available knowledge regarding it. The primary paper referenced in this document, "Mesothelioma: You Do Not Have to Work for it," written by Elizabeth J. Ampleford, Ph.D., and Jill Ohar, M.D, has summarized the results of the previous studies while providing case studies of three women who developed asbestos-disease from bystander exposure.

One study they referenced showed an increased risk for pleural mesothelioma from both environmental exposure and household exposure. The former showed a 10-fold increase over the non-exposed control group while the latter showed a 5-fold increase. Another study demonstrated that when comparing mesothelioma patients to a control group of patients with another form of asbestos-disease, women were disproportionately more represented in the mesothelioma control group. These studies, among others, show that mesothelioma from bystander exposure to asbestos is a problem with serious public health repercussions-especially for women. In fact, one study showed that a shorter length of exposure, which would be the case with a bystander exposure, was not necessarily indicative of a lower disease risk if a high concentration of fibers was present.

Pleural Mesothelioma Bystander Exposure: Mrs. X

Ampleford and Ohar describe the case of Mrs. X, a 63 year-old woman without any known occupational exposure to asbestos. She did, however, spend most of her life in a neighborhood with a cement factory that manufactured a cement pipe containing crocidolite asbestos. The factory produced 10-20 tons of waste per day. Her father, as well as three uncles and an aunt, worked at this factory. She would meet her father for work for lunch and ride around the plant grounds on a bike and when she became a teenager she would assist in laundering her father's clothes. Years later, she presented with a right pleural effusion that was later diagnosed as malignant mesothelioma, epithelial type.

Lung Cancer Bystander Exposure: Ms. Y

Ms. Y was a 51 year-old woman who, like Mrs. X, did not have any occupational exposure to asbestos. She worked as a medical assistant in a hospital environment, where one would expect as clean of air quality as possible. Her bystander exposure came from the same cement factory that Mrs. X father and family worked at. In fact, Ms. Y lived quite close to Mrs. X for most of her life. She can remember "the grass in her yard, the tomatoes in the garden and the cars in the driveway constantly having a white dust on them. As a child, she remembers wiping the white dust from her bicycle and how the silt would build up on her bedroom furniture."

The white dust was asbestos.

At least two of her siblings without occupational exposure to asbestos developed asbestosis and another developed asbestosis and asbestos-induced pericarditis. When Ms. Y complained of chest pain in February of 2000, a chest x-ray raised the possibility of lung cancer that a subsequent PET scan confirmed. Aside from the tumor, significant chest scarring and pleural plaques were noted and a fiber burden analysis conclusively showed the presence of crocidolite fibers in a concentration consistent with occupational exposure-even though Ms. Y had no occupational exposure to crocidolite. Her environmental exposure was so great that her body presented with levels associated with occupational exposure.

Studies have shown a remarkable correlation between patients with disease from bystander exposure and family members with other forms of cancer. One study reported that 33% (17/52) of women with mesothelioma from bystander exposure had a parent with cancer. Another showed an increased frequency of close relatives with cancer among patients with primary or bystander mesothelioma. It is not insignificant to note Mrs. X's other family members (three uncles, an aunt) who worked at the cement factory each developed a form of cancer.

Peritoneal Mesothelioma Bystander Exposure: Miss S

Unlike Mrs. X or Ms Y, Miss S did not have a bystander exposure from environmental contamination from a large factory. Miss S's exposure came from exposure to asbestos fibers on her father's clothes. Mr. S worked a variety of jobs with heavy asbestos exposure and he and his wife washed his clothes at home. His wife noted that dust debris would build up on the floor of their washroom. Miss S would, on occasion, help with the washing of clothes.

Miss S was born prematurely between 28-30 weeks of gestation and stayed in the hospital for three months after being born. She had a patent ductus-arteriosis closed after birthing, bilateral chest tubes inserted when she was four because of a "pulmonary infection," hydrocephalus and mild cerebral palsy. During a physical examination at age 22, a pelvic mass was discovered and a subsequent CT revealed extensive abdominal ascites and other non-standard peritoneal findings. Upon admission, a chest x-ray showed scarring and rib abnormalities, a pathology test reported a finding of malignant mesothelioma, epithelial type and the pelvic mass was discovered to cover almost the entire peritoneal surface.

Miss S stands out as an exceptional case of peritoneal mesothelioma. Her age places her among the youngest patients diagnosed with mesothelioma. Studies on asbestos exposure during fetal development and early childhood reveal that exposures occurring during these critical development times may lead to the development of more aggressive tumors. One study documented the presence of asbestos fibers in placental tissue from health newborns, as well as fibers in the "lung, liver, skeletal muscle and placenta of stillborn infants." Ampleford and Ohar suggest that the results of this study may indicate that Miss S was actually first exposed to asbestos in utero.

Conclusion

The authors conclude their paper by suggesting that although regulations regarding asbestos use have helped protect people from occupational exposure, bystander exposure is still a serious concern and that medical professionals need to be on the lookout for mesothelioma in populations who do not evidence any primary exposure to asbestos.

Labels: mesothelioma