Constructing melanopic light exposure profiles from sparse daily-route measurements.

Abstract

Daily light exposure is temporally structured, yet calibrated spectral measurements are usually available only at selected locations and times. Turning such a sparse library into a schedule-resolved profile requires an assignment rule: a decision about which measurements may represent each unmeasured part of the day. We examined how much that decision matters. Sixty-three eye-level spectral irradiance measurements, collected across home, commute, office and lunch settings on three June days in Ottawa, were mapped onto a schedule of 22 half-hour slots. For each of six assignment rules we generated 100,000 profiles and computed melanopic dose and time above thresholds of 250, 1,000 and 10,000 melanopic lx. Indoor-only and outdoor-only assignments gave contrasting bounds, with median doses of 16,536 and 119,995 lx ⋅ h. Among the four rules that combined indoor and outdoor measurements, median dose varied only from 44,257 to 48,337 lx ⋅ h, whereas the central 95% of the generated dose distributions spanned ranges differing by nearly a factor of two. Central estimates were set largely by the composition of the eligible measurement pools rather than by the structure a rule preserved; the rule mainly determined spread. Targeted substitutions, in which only commute and lunch conditions were changed, raised median dose by 28,600 lx ⋅ h, with outdoor lunch contributing more cumulative dose and outdoor commuting more time above 10,000 lx. The framework supports sensitivity and scenario analysis rather than reconstruction of continuous personal exposure, and shows why the assignment step must be reported explicitly for a constructed profile to be interpretable.