Concerns about environmental and technological changes affecting health have been shown to be associated with symptom reports in cross-sectional studies. We aimed to investigate how worries about modernity affecting health, negative affectivity, and prior symptom complaints influence health complaints after environmental spraying in a prospective study. Two hundred ninety-two residents of West Auckland completed questionnaires measuring recent symptoms, negative affect, and concerns about the effects of modernity on health before aerial spraying of their neighborhood with Foray 48B. After spraying, 181 residents (62%) returned a follow-up questionnaire measuring symptoms, spray-avoidance behavior, and the perceived effect of the spray program on health. The number of symptoms reported after the spray was most closely related to the number of symptoms reported at baseline (beta = 0.40, p = .0001). Higher levels of modern health worries (beta = 0.23, p = .001) and baseline symptoms (beta = 0.17, p < .05) were associated with a higher number of symptoms being attributed to the spray program. Modern health worries also predicted avoidance behavior during the spraying times (beta = 0.32, p = .001) and the belief that the health of participants and the health of their children and pets was affected by the spray (all p < .01). Worries about aspects of modern life affecting health can strongly influence the attribution of symptoms and beliefs about health effects after environmental incidents.