P_e =exponent of the excess risk function;A₀ =standard age at first exposure; L=standard exposure duration;Y₀ =first year of occupational exposure to asbestos; Y₁ =year that the rate of increase of the mean exposure concentration per generation began to accelerate (see fig 3);λ=ratio of the mean exposure concentration for the generation that began working in the yearY₁ and the concentration for the most exposed generation (E_max );Y₂ =year that the first of the most exposed generations began working;Y₃ =year the last of the most exposed generations began working.