For practical purposes, therefore, HSE assumes that no such "safe" threshold exists. Others have noted as well that there is no evidence of a threshold level below which there is no risk of mesothelioma. There appears to be a linear, dose–response relationship, with increasing dose producing increasing risk of disease. Nevertheless, mesothelioma may be related to brief, low level or indirect exposures to asbestos. The dose necessary for effect appears to be lower for asbestos-induced mesothelioma than for pulmonary asbestosis or lung cancer. Again, there is no known safe level of exposure to asbestos as it relates to increased risk of mesothelioma. The time from first exposure to onset of the disease, is between 25 and 70 years. It is virtually never less than fifteen years and peaks at 30–40 years. The duration of exposure to asbestos causing mesothelioma can be short. For example, cases of mesothelioma have been documented with only 1–3 months of exposure. Occupational
Exposure to asbestos fibers has been recognized as an occupational health hazard since the early 20th century. Numerous epidemiological studies have associated occupational exposure to asbestos with the development of pleural plaques, diffuse pleural thickening, asbestosis, carcinoma of the lung and larynx, gastrointestinal tumors, and diffuse malignant mesothelioma of the pleura and peritoneum. Asbestos has been widely used in many industrial products, including cement, brake linings, gaskets, roof shingles, flooring products, textiles, and insulation.Commercial asbestos mining at Wittenoom, Western Australia, took place from 1937 to 1966. The first case of mesothelioma in the town occurred in 1960.
The symptoms may start appearing as early as a few hours after birth and up to three months of age. Around three-fourths of affected children present with neonatal seizure. Other seizure types such as focal or generalized tonic seizures, epileptic  spasms or other epileptic manifestations may occur at the course of the disease. The distinctive feature of the phenotype is severe progressive encephalopathy with delay in development and abnormal neurological examination delay (hypotonia, lethargy, poor eye contact, difficulties in feeding) usually being present even before the onset of other symptoms. Head circumference is usually normal at onset but microcephaly may develop over time. Family history is usually normal. Causes
There are varied etiologies related to EME that are mainly genetic abnormalities (mutations), brain structure abnormalities, or inborn metabolic defects. Another common reason rather than structural brain abnormality is inborn metabolic defects. Sometimes a metabolic disorder that affects how the brain works may lead to EME. While most of these metabolic disorders cannot be reversed, sometimes treating the underlying disorder can help. Vitamin-responsive epileptic encephalopathies are rare but significant reasons. Genetics
A growing number of genetic aetiologies have been linked to the phenotype of EME and Otahara syndrome and diagnosis by genetic testing can nowadays be achieved in around 50 percent of cases. Some examples of well described genetic aetiologies include: KCNQ2- DEE. • SCN2A-DEE • STXBP1-DEE. • CDKL5-DEE• KCNT1-DEE and UBA5-DEE. Acquired
No acquired aetiologies are known for EME although etiology remains unknown for a small percentage of patients after genetic, metabolic, and imaging workup.